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Intelligent discovery, configuration and composition of devices in a

1. uq us enum right l l Contained in the device description presented are placeholders for a series of annotations empty square brackets These refer to concepts that emerged during investigation of terms for the taxonomy and are yet to be covered They broadly align to indicating resource availability where driver code interfaces accord with device structures linking to device state and a series of enhancements relevant to the conduct of composition Consequently they are presented in the next chapter in the sections where they impact the matching process 100 Refining Task Elements Further elaboration is required on the special role task elements play within a device They evolved from a term in the taxonomy through to their use in a device description With logical representation of devices decided upon we can elaborate on patterns to their functionality and move towards completing the picture of a structural type An observation concerning prior work on task analysis is that granularity to description determines the sorts of tasks that could be implemented For example Miller s Task Strategies Approach Fleishman Quaintance et al 1984 adopted a human cognitive processing model which resulted in many tasks being involved and was less specific about the exact functionality described Whereas we have established the level of analysis at a low level with definite operations describable for each
2. dac_volume_up command uq us enum increase_audio_out_volume The reference to dac_volume up is used as a reference to device facts indicating adjustments to be used when applying or removing a match result stateAdjust imic2 dac_volume dac_volume_up apply Q U R V Q U R NewV NewV is V 10 stateAdjust imic2 dac_volume dac_volume_up remove Q U R V 0Q U R NewV NewV is V 10 Additionally state itself is asserted as a fact as a device is prepared for operation state imic2 dac_volume ratio decibel An example at the leaf level is an annotation appearing with audio_out_mute aspect inside the 1st square bracket in a structural description task_element te1 adjust_mute task O O i function lt ADJUST gt ute audio_out_mute system boolean true signal_m The audio_out_mute annotation will be returned in the results and combined with the value correspondence to adjust state when applying the match with a device 126 Goal expression When application or removal of a match result happens the facts denoting state are modified by trying the executeStateAdjust goal using the annotations contained in the match result and supplying a mode apply or remove executeStateAdjust _ _ _ executeStateAdjust Mode Element Spec SAH SAT state Element StateID V use supplied p
3. JE EJ Headphone Volume TE EY T UH El El UT data wheel dial audio output port RCA x 2 audio output port stereo headphone Head Phone Level potentiometer Midi Out LED Midi Out port Midi In port on off Midi In LED Ul U1 T u MASTER fader slider fader NULL switch SOLO mute toggle switch RECord ready switch LOCATE lt lt switch LOCATE gt gt switch SET switch BANK lt switch BANK gt switch REW transport ctrl switch F FWD transport ctrl switch STOP transport ctrl switch PLAY transport ctrl switch RECORD transport ctrl switch figure A 6 Tascam US 224 device structure 155 A 1 4 Task Element Comparison illustrative sample only module task_element TE category task subcategory function aspects direction sampling rate KHz data_channels bit_resolution analog finite _impulse_response_filter analog low_pass_filter analog antialiasing filter analog _dynamic_range dB analog signal to _noise_ratio dB analog total _harmonic_distortion digital high pass_filter digital linear_causal_filter digital_decimation_filter odif_stop_band_attenuation dB odif_pass_band_ripple dB oversampling digital interpolation_filter module task_element TE category task subcategory function aspects direction sampling rate KHz data_channels bit_resolution analog finite_impulse_response_filter analo
4. Whereas at the leaf level stating as a goal binds NewMatchTerm RQTermName OldTerm NewTerm NewMatchTerm In either case success occurs should the device fact exist in the database and NewZerm can be bound Otherwise failure leads to a null result 118 5 2 Process Enhancements Flexibility is added to composition by drawing upon a range of enhancements related to the problem domain of devices The objective is to allow participants to tailor how searching proceeds and which details are included in the results This is accomplished through annotations to the structural descriptions associated with requests and devices Annotations encountered during traversal are used to reference database assertions associated with either or both participants A range of enhancements provide for the following capabilities 1 automatic arbitration of access to device elements automatic configuration of access to code interfaces recording match parameters for use when accessing devices quantitative correspondence at the lowest level Managing participant state as results are applied or removed using match conditions to check a sub match Nn BW WN Each of these augmentations is explained in terms of the structures involved and their treatment during the match process The intention behind our design choices is discussed Finally an applied example is selected to motivate the need to enhance composition 5 2 1 Arbitrating Ac
5. gt gt gt gt gt gt gt try another DGroup dgroup21 from Device green_2 us224_1 FEE EEE ETE EE ETE EEE EEE EEE EEE EEE EE EEE EEE EEE EE EEE EEE EE EEE EE FHELETEET ETE ET EEE ET EEE ET EEE ET EE EET ETE EEE TE ETE TEETH EP Et ttt checking have an acceptable RQGroup match comparing match factors is gt 42 gt gt gt gt gt gt gt try another DGroup dgroup22 from Device green_2 us224_1 FATEH EET TEE ETT EEE EEE ET EEE EEE ETE EE EEE EE EEE EEE EEE EET gt checking availability of Registration Unit analog_audio_stream_in available term direction matched value uq us enum Lanalog_to_ Ee A term sampling_rate matched value frequency hert A term data_channels matched value system integer term bit resolution matched value system HRA accept Submatth nateh Factor check S M C SC term function A term principal matched value uq us enum convert M C SC term role M C SC term task accept submatch match factor check 14 gt 14 M C SC term task element A term direction matched value ug us enum unidirectiong 1 A term logical_channels matched value system integer 2 A term signal_fornat matched value ug ys enum digital term model matched value ug us erum strean accept submatch match factor checi M C SC term Link A term compression matched value uq us enum uncompressed A term data format matched value yq us enum pem_audio acce
6. It consists of a processing box attaching to a computer system via the USB interconnect Externally the box has a range of Audio IN and OUT ports both analog and digital plus MIDI IN OUT to which attach audio sources and destinations It requires external power source to be connected There are various knobs for adjusting analog output levels Device Description Internally the M Audio Audiophile comprises a range of chips for which there are published datasheets Texas Instruments 1999 Asahi Kasei Microsystems Co 2004 Cirrus Logic 2005 Collectively these provide coverage for generating the following Device Structure a series of groups each comprising a range of modules group 13 general G task elements TE type control source 11 Digital to Analog Converter convert USB Control 11 DAC Mute adjust USB Control 11 Line Out Volume adjust UI Line Out Level 11 Head Phone Volume adjust UI HeadPhone Lvl 12 Analog to Digital Converter convert USB Control 12 ADC Mute adjust USB Control 14 Audio Stream IN OUT transform n a 14 USB IN OUT director n a 14 USB Control transform n a 15 Midi IN OUT transform n a 150 16 DDC In 16 DDC In Mute 17 DDC Out 17 DDC Out Mute user interface UI 11 Line Out Level 11 Head Phone Level 18 Power Switch 18 Power LED communication link CL 11 Digital OUT to DAC 11 Analog OUT from DAC RCA 11 Analog OUT from DAC Head Phone 12 Digital IN from ADC 12 Anal
7. MacKinlay J D amp Robertson G G 1991 A Morphological Analysis of the Design Space of Input Devices ACM Transactions on Information Systems vol 9 2 DOI 10 1145 123078 128726 pp 99 122 Carroll J M amp Kellogg W A 1989 Artifact as Theory Nexus Hermeneutics Meets Theory Based Design In Proceedings of the SIGCHI Conference on Human Factors in Computing Systems CHI 89 DOI 10 1145 67449 67452 pp 7 14 Cheshire S amp Steinberg D H 2005 Zero Configuration Networking The Definitive Guide O Reilly amp Associates ISBN 0 596 10100 7 184 Chou A Yang J Chelf B Hallem S amp Engler D 2001 4n Empirical Study of Operating Systems Errors In Proceedings of the 18th ACM Symposium on Operating Systems Principles SOSP Banff Alberta Canada DOI 10 1145 502034 502042 pp 73 88 Cirrus Logic 2005 CS8427 96kHz Digital Audio Interface Transceiver datasheet DS477F3 Clipsal Integrated Systems 2005 Your home smart home smart living Clipsal Australia viewed March 2014 lt www clipsal com cis gt Compaq Inc Hewlett Packard Inc Intel Microsoft Corporation NEC amp Phillips 2000 Universal Serial Bus USB Specification revision 2 0 standard Compaq Connor R 1990 Types and Polymorphism in Persistent Programming Systems Department of Mathematical and Computational Sciences PhD thesis University of St Andrews St Andrews Fife UK Connor R Brown A B Cutts
8. only approach device based structures are consulted to determine requirements refer to address map determination under configuration space for PCI PCI SIG 2002 205 8 A platform level provisioning follows and involves recording logical resource allocations back with the device A complete picture of how resources have been apportioned across all attached devices is captured in a tree structure handed over to the operating system as platform configuration code yields control 17 Resolving whether a system is viable depends on arriving at a conflict free allocation of logical resources be that apportioning regions of memory or allocating interrupt signal lines The requirement for logical resource provisioning acts to break device independence through reliance upon external software for an essential element This is exacerbated by platform configuration code needing to be aware of which interconnect to ensure provisioning appropriate driver code to even locate the device and permit minimal device access In earlier systems physically setting switches on devices themselves accomplished resource assignment to permit access and signal events The particular requirements varied across interconnects but required manual determination of a conflict free system configuration refer to background to developing software approaches to replace physical switch settings Intel and Microsoft 1994 An early example of device based assignment is that of sys
9. uq us enum uncompressed A term data_format matched value uq us enum pcm_audio accept submatch match factor check 6 gt 5 M C SC term channel M C SC term primitives accept submatch match factor check 12 gt 9 M C SC term communications_Link HEHHEHE HHHH HHHH HHHH HHHH EE EET EET EEE HHHH TEETH Ett ett tt checking have an acceptable RQGroup match comparing match factors is 40 gt 32 a M C M C RQGroup match found with DGroup dgroup11 from Device blue_3 audiophile_1 adding match for RQGroup rqgroup2 to match list for Request rq1 apply match with Device blue_3 audiophile_1 MODE apply Request Group rqgroup2 Device Group dgroup11 registration units analog_audio_stream_out updated gt unavailable state update term bit_resolution maps gt state dac_resolution new value system bit 16 amp retained value system bit 16 state update term data_channels maps gt state dac_channels new value system integer 2 amp retained value system integer 2 state update term sampling_rate maps gt state dac_sample_rate 178 new value frequency hertz 48000 amp retained value frequency kilohertz 44 1 completed applying RQGroup match to Device to constrain resource availability gt completed matching entire RQGroup list for Request rq1 X checking have derived a match for Request rq1 adding match for Request rqi to match list for Request Alternati
10. 1 0 connector ill ug us enum direction uq us enum mini_stereo_socket output Lcommunications_ link primitives 1 1 l link 1 1 Hi direction ug us enum logical_channels 1 system integer enum I I l 1 i unidirectional 1 2 signal_format ug us enum analog model ug us enum stream lcommunications link 1 1 1 primitives 1 1 ey channel channel1 uq us enum data_format system bits enum data_width data_rate system hertz enum 1 0 0 01 pcm_audio 8 16 32000 44100 48000 fchannel channel2 tink 0 0 0 direction uq us enum signal_format uq us enum 1 0 1 001 Tiss 1 01 11 ua us enum 1 1 ug us enum unidirectional digitall task_element task 1 function direction rote principal bere rl l l 1 digital_to_analog convert deviceGroup imic2 AS task_element ll 1 011 1 01 electrical interface communications_link eA A A O task_element 1 01 01 communications_link il user_interface 103 4 4 3 Determining Equivalence We defined structural types for devices
11. 2002 The uncovering of physical details extends to engineering outlines permitting embedding of devices as part of a system platform These appear in the specifications for interconnect chipsets and include discrete devices embedded in a system design refer to appendix on mechanical details of Matrox G400 graphics chip specification Matrox Graphics 1999 Additionally the user manual accompanying a device contains information of relevance to operating a device from the physical dimensions and weight through to the manufacturer s recommended operating conditions Even overviews provided in a product brochures provide greater descriptive information on a device than can be gleamed at the logical level refer to physical dimensions appendix of Tascam US 428 audio controller manual TEAC 2007b The PCI specification PCI SIG 2002 illustrates a decomposition of engineering specifics into a mechanical electrical and bus operation level These are detailed in figure 4 6 along with an indication of the relevant aspects A Mechanical level i physical dimensions with tolerance values connector arrangement form factor of the connector and card spatial restraints upon card to facilitate attachment to a computer system il physical description 32 or 64 bit connector type 3 3 or 5V power signaling environment keying iii physical requirements connector casing and card materials contacts materials iv physical performance contact dur
12. 2003 The extensive array of services is presented in figure 2 6 and must be implemented fully in order to encapsulate the driver and create the illusion that a different kernel is present This provides a succinct overview of the dependency as it stands in a current operating system The nature of this dependency is best understood in terms of the evolving nature of device related code Prior to the emergence of drivers as loadable units any i o related code was an integral part of an operating system kernel With the advent of interconnects capable of accepting any device controller that adhered to their specification the tight coupling of an operating system to the hardware was broken This led to providing additional code after the operating system had been developed for a target system in order to make sense of the new device This is characterised by the RT 11 operating system for the PDP 11 series computer systems It handles particular devices connecting to Unibus via code distinct from the kernel and separately loadable Digital 1984 19 Interrupt Handling e Request Release Interrupt e Initalize IRQ handling e Get IRQ thread number Memory Management e kmem Allocation Deallocation e vmem Allocation Deallocation e nitalize LMM pools and initial regions Address Conversion Linux __va __pa macro replacements Page Allocation Deallocation mapping knowledge addresses amp sizes remains in drivers Slab Caches introduc
13. 23 Head Phone Volume adjust UI HeadPhone Lvl 153 user interface UI 22 Line In Level A B potentiometer 22 MicLineGuitarSwitch A B switch 22 InputSignalLED A B LED 22 InputOverloadLED A B LED 23 Line Out Level potentiometer 23 Head Phone Level potentiometer communication link CL 22 Digital IN from ADC PCM Audio 23 Digital OUT to DAC PCM Audio electrical interface EI 22 Analog IN Phone A B 0 25in mono jacks A amp B 22 Analog IN XLR A B XLR connectors A amp B 23 Analog OUT RCA RCA jacks x2 23 Analog OUT Head Phone 0 25in stereo jack NOTE not all modules included in description refer to logical overview for a more complete outline of the device Device Code Interfaces DCI Digital to Analog Converter select sample rate resolution channels Analog to Digital Converter select sample rate resolution channels DAC Mute ADC Mute Registration Units RU set mute on off set mute on off Audio Stream Out Analog x 1 associated with TE DAC Audio Stream In Analog x 1 associated with TE ADC Device State initial values ADC DAC AnalogIN Mute AnalogOUT Mute sample rate 44 1kHz resolution 16 bit channels 2 sample rate 44 1kHz resolution 16 bit channels 2 set to off set to off 154 Device Logical Overview UI UI amp DDC Out ce power power a nes transfor switch LED CL TE rCM transfor audio n INPUT MONITOR ie on off U I signal threshold exce
14. 96000 audioSetting _ _ _ _ _ _ _ _ _ _ 48000 audioSetting _ _ _ _ _ _ _ _ _ _ 44100 audioSetting _ _ _ 1 _ _ _ _ _ _ _ 48000 audioSetting _ _ _ 1 _ _ _ _ _ _ _ 44100 audioSetting _ _ _ 2 _ _ _ _ _ _ _ 48000 audioSetting _ _ _ 2 _ _ _ _ _ _ _ 44100 audioSetting _ _ _ 3 _ _ _ 16 _ _ _ 44100 audioSetting _ _ _ 3 _ _ _ 16 _ _ _ 48000 The goal refers to constraints expressed as facts which are based on the device discussed in the example above It also contains a helper goal service SubmatchValue which is supplied by the match process to extract leaf level values from a sub match as follows 128 service_SubmatchValue Value TermList SubMatch service_SubMatchAV Value TermList SubMatch service_SubmatchThenState _ _ _ fail service_SubMatchAV _ _ fail service SubMatchAV AV T SMT sss service_SubMatchAV Value LeafTerm _ LeafTerm _ _ Value Goal expression During the traversal of a structural description in the goal WalkRQGroup refer to the section guiding the search for elaboration a check is made of match conditions from either participant prior to adding sub matches to the results This is accomplished by trying the goal executeMatchConditions with the list taken from the annotation mentioned above executeMatchConditions _ _ _ executeMatchConditions Participant
15. M C SC term characteristics A term Classification matched value ug us enum external A term classification matched value ug us enum external FHEPETEET ETE ETHEL HHHH HHHH EEE TEETH EE HHH HHHH checking have an acceptable RQGroup match comparing match factors is 26 gt 42 M M ERROR no match found for RQGroup rqgroup1 with Device red_1 imic2_1 reversing application of group matches so far with same device aborting Request List at rq1 amp returning null match X checking have derived a match for Request rq1 ERROR no match found for Request rq1 reversing application of matches for prior requests with respective device s aborting Request Alternative composite_rql amp returning null match X checking have derived a match for Request Alternative composite_rql gt gt gt try another Request Alternative composite_rq2 at priority 75 with Request list rq2 rq3 next Request rq2 with RQGroup list rqgroup1 gt gt gt gt gt try another Device red_1 imic2_1 next RQGroup rqgroup1 gt gt gt gt gt gt gt try another DGroup dgroup1 from Device red_1 imic2_1 HEHHEHE HHHH HHHH HHHH HHHH EE EET ETE TEETH EEE TEE TEEPE TEE Et FHEPETEAT ETE ETHEL EEE ET EEE ET EEE EEE ETE TEETH EEE TEE EE EP ET Ett checking have an acceptable RQGroup match comparing match factors is gt 42 gt gt gt gt gt gt gt try another DGroup dgroup2 from Device red_1 imic2_1 FEFELEE ELE ELE EL
16. Motivation A further intention is to place constraints on the match process by allowing the participants to specify verification goals These concern whether a sub match is to be accepted for inclusion in the results and express checks deemed relevant to either participant These could involve state value correspondence in the results or the presence of terms in the sub match Illustrative example The motivation for condition checking is best illustrated with an applied example of the constraints underpinning operation of an audio codec control surface device the M Audio Audiophile USB M Audio 2006 Its connection to the computer system for streaming 127 audio is via an interconnect with a maximum data transmission rate related to the USB 1 1 full speed specification Compag Hewlett Packard et al 2000 Allocation of communication links to or from the device s audio codecs requires considering multiplexing Separate high quality audio requests for each of these audio links analog in out digital in out may be submitted for matching except that should all links be allocated at the highest quality the data transfer rate across the interconnect would exceed its maximum capacity Hence a check must be made of the current allocated capacity plus audio link quality in the new match against a constrained maximum for the device Technicals Where a match condition is annotated in a structural description it references an accompan
17. RU Audio Stream Out Digital x 1 associated with TE DDC In implicitly arbitrates logical access to DDC In Mute Audio Stream Out Analog x 1 associated with TE DAC implicitly arbitrates logical access to DAC Mute Audio Stream In Analog x 1 associated with TE ADC implicitly arbitrates logical access to ADC Mute Audio Stream In Digital x 1 associated with TE DDC Out implicitly arbitrates logical access to DDC In Mute Midi In Out x 1 associated with TE MIDI IN OUT Device State initial values ADC sample rate 48kHz resolution 16 bit channels 2 DAC sample rate 48kHz resolution 16 bit channels 2 ADC Mute set to off DAC Mute set to off DDC In Mute set to off DDC Out Mute set to off Device Logical Overview Line Out level Line Out potentiometer volume DAC Mute ve TE T convert E ae ouput PCM ji ro USB Audio Stream i TE BoR HeadPhone headphone audio output port x2 RCA Port IN OUT q IN OUT audio Head Phone BU TE TE ransform Level A P CM potentiometer audio MIDI Wo ADC audio input TE Mute Ely port x2 transfor RCA audio input USB Control Ely port x2 TE 1 4 Unbalanced transform p gt M DDC Out TEM ae Ta TE audio ee output TE TE cl copied S PDIF DD DTS audio CL DDC In PCM s n V B audio audio input power cL TE CL port connector TE a S PDIF coaxial S PDIF Midi Out power power CL switch LED midi port Midi In CL Ely port
18. Spec SubMatch MCH MCT use supplied parameters with univ operator to check for existence then try matchCondition goal Term matchCondition Participant Spec SubMatch MCH Term executeMatchConditions Participant Spec SubMatch MCT 129 5 3 Guiding the Search A reasoning procedure is necessary to know how to derive correspondence The search strategy chosen pursues satisfaction of requests based on their structure and on guidance regarding what constitutes satisfaction In the preceding chapter we defined the structure of a request and a device Not only were data structures defined but also the steps by which correspondence is to be checked and satisfaction achieved As a set these guidelines start with a request alternative and progress through to detailing the traversal of a structural description They describe how a device is to be checked and how to systematically try a request We implemented the guidelines in Prolog by expressing them in constraint logic Their significance to composition is explained including an indication of how they constrain the search A high level outline of the steps involved accompanies the presentation of goal logic and helper goals 5 3 1 Satisfying a Requester s External Access Point Guidance on satisfying a requester s external access point affects the highest level of the process and acts to constrain how multiple alternatives are matched How did it come about Without l
19. a j o oO 7 me z 2 i nemmen 5 amp i JE Seo oS E sane HEHE Gaari E x4 E figure 5 1 audio channel strip arrangement for Tascam US 224 audio control surface devices A request for multiple channel strips would necessarily be expressed as repeats of a RQGroup describing a single channel However the process will always match to the first strip no matter how many are sought in the same request We workaround this issue by applying match results with a device before proceeding any further More precisely as each RQGroup match is found the results are applied to the device bound to the current request This adjustment is isolated to the match process and does not affect the distributed system Application during the process is speculative because the device may be rejected should another alternative need to be tried As such capturing a picture of the device s resource availability and state is necessary prior to any alterations This is accomplished by making a copy of those assertions Then results are applied to provide a dynamic picture 135 of the availability of access as each RQGroup is satisfied Restricting access forces the process to continue searching and find correspondence with other DGroups or further devices as other requests are tried Should a request or even an alternative be rejected later in the process reference is made to the original device assertions to reverse the
20. match process again Stage 3 Match Expectations e re submission of outlets with partial matches from Requester 1 e lack of a requested Electrical Interface module on 2nd Device precludes a highest priority match e however availability of both in out audio streams leads to better match than existing e an improved match forces cancellation of existing amp application of the new match result e Ist Device reflects freed up resources after cancellation for Outlet outlet1 Active Request Alternative composite_rq4 25 Request Alternative List composite_rq1 100 composite_rq2 75 composite_rq3 50 composite_rq4 25 composite_rq5 20 gt gt gt try another Request Alternative composite_rql at priority 100 with Request list rq1 next Request rq1 with RQGroup list rqgroup1 rqgroup2 gt gt gt gt gt try another Device red_1 imic2_1 next RQGroup rqgroup1 gt gt gt gt gt gt gt try another DGroup dgroup1 from Device red_1 imic2_1 HEHHEHE HHHH HHHH HHHH HHHH ETET PETE EE ETE ETE TEETH EE ETE Et FHELET EEL ETE ETHEL EEE ET EEE ET EEE EEE ETE E EET ETE TEETH EEE t ttt checking have an acceptable RQGroup match comparing match factors is gt 42 gt gt gt gt gt gt gt try another DGroup dgroup2 from Device red_1 imic2_1 HEHHEHE HHHH HHHH HHHH HHHH EEE ETE ETE TEETH ETE TEE EEE PETE EEE gt checking availability of Registration Unit audio_stream_out available A term samp
21. matchOutletToDevices Requester Outlet _ where unable to satisfy any alternative return without performing further actions getExistingMatchPriority no pre existing match getExistingMatchPriority _ ActiveCompRQPriority ActiveCompRQPriority Matching requester s external access point helper goals When trying goal matchOutletToDevices detailed above the result becomes final once it passes the check for a non null match It is then that any pre existing match is cancelled by trying the goal cancelExistingCompRQMatch Finally the match can be applied to the requester and the match stored in the database by trying applyCompROMatchToRequester All of these goals appear below app lyCompRQMatchToRequester app lyCompRQMatchToRequester MLH MLT loop to apply each group match with Requester app lyRQGroupMatchListToRequester MLH app lyCompRQMatchToRequester MLT applyRQGroupMatchListToRequester app lyRQGroupMatchListToRequester MLGH MLGT Requester Out Let CompRQ RQ RQGroup Device DGroup GMF SubMatch MLGH remove backed up state to complete application with Device retractall state Device _ _ shadowed then apply match results with Requester applyMatchWithRequester apply MLGH insert match result for group into database assert matchTransaction MLGH applyRQGroupMatchListToRequester MLGT cancelExistingCompRQMatch _ _ cancelExistingCompRQMatch Requester Outle
22. power source and sink requirements differ across device classes from root ports host and self powered hubs to low and high powered devices plus self powered devices Supply however may only be delivered to downstream devices from the host The concept of unit load is used for management and redefined in later specifications for 83 SuperSpeed 150mA Notions of low and high power draw are expressed in terms of unit loads 1 for low amp up to 6 for high Restrictions are placed upon devices when suspended up to 12 5mA and at low draw which is stipulated as the initial powered mode Transition to high draw is under driver control which is assigned responsibility for ensuring the availability of power Hewlett Packard Intel et al 2011 The PCI specification stipulates the maximum power draw allowed of any connected device 25watts and devices are not to source power back to the interconnect Then assuming system platforms will not provide such to each connector the specification recommends devices power up in a reduced power state consuming at most 10watts While in this state devices must provide access to their PCI Configuration Space containing device identity and are required to perform boot related functions as instructed Driver code is left with the responsibility for managing power consumption and enabling full power use refer to 4 4 2 2 Power Consumption PCI SIG 2002 Finally the recently introduced Thunderbolt in
23. principally integer float and UTF 8 is an example of such an extension Pike and Thompson 1993 Unicode 2000 The checking of values is grounded in the use of the current standard metric system the International System of Units SI This are expressed as goals providing for e verifying measurement quantities as a baseline e g length cannot be compared to electrical current e converting symbols to the same units of measure e g converting lengths expressed in millimetres or centimetres to metres e checking the extent to which values correspondence with reference to the ranges specified e g evaluating whether any overlap exists between two ranges possibly expressed as a range of values Illustrative example An illustration of quantitative correspondence is that of seeking a simple audio codec device similar to the Griffin iMic2 Griffin Technology 2010 that can provide an audio out signal for a pair of headphones A request for converting digital audio to an analog signal can be specified as a task_element module then task category function subcategory and sampling rate data_channels plus bit_resolution aspects It is the addition of the quantitative though that illuminates the details regarding the capability to perform the signal conversion task This is accomplished by specification of a range of unit values for each aspect such as a sampling rate in hertz of either 44100 or 48000 Correspondence sought is then a matter of
24. rca_connector rca_connector A term classification matched value Cig us enum Fexternalj A term device boundary matched value syst m bodlean true M C SC term relation M C SC term logical_structure A term connector matched value ug us enum rca_connector rca_connector A term classification matched value ug us enum fexternal A term device boundary matched value syst m boolean true M C SC term relation M C SC term logical_structure A term width matched value Clength mm 8 37 M C SC term physical_dimensions M C SC term physical_manifestation A term connector matched value uq us enum rca_connector rca_connector A term classification matched value ug us enum external T A term device_boundary matched value syst m bodlean true M C SC term relation M C SC term logical_structure A term connector matched value uq us enum rca_connector rca_connector A term classification matched value ug us enum external A term device boundary matched value syst m bodlean true M C SC term relation M C SC term logical_structure FEFELEP ELE PELE ET EE ETE ETE EET EE ETE EET EEE TEE ET EET Ett ett ttt checking have an acceptable RQGroup match comparing match factors is 26 gt 42 gt gt gt gt gt gt gt try another DGroup dgroupi2 from Device blue_3 audiophile_1 HEHHEHE HHHH HHHH HHHH HHHH HHH TEETH TEETH EEE TEETH EE ETE Et A term operate ma
25. signal_mute matched value system boolean true C SC term function A term principal matched value uq us enum adjust C SC term role C SC term task A term configure matched value uq us enum required A term operate matched value uq us eum Pequired M C SC term approach M C SC term control z accept submatch match factor check 14 gt 10 M C SC term task element A term data_format matched value uq us enum analog A term connection establish matched value ud us enum hot_pLuggable accept submatch match factor check 3 gt 2 M C SC term electrical M C SC term characteristics A term direction matched value ug us enum input A term classification matched value L q us enum Ce A term direction matched value uq us enum input A term classification matched value uq us enum external A term signal_ended matched value ug us enum nbal anced A term data_format matched value uq s enum analog A term connection establish matched value uq us enum hot_pluggable ccept submatch match factor check 4 gt 2 SC term electrical SC term characteristics A term direction matched value uq us enum input A term classification matched value uq us enum external A term direction matched value ug us eAum Linp t A term classification matched value uq us enum external A term data_format matched value ug us enim ahalog
26. task ahead is to articulate the properties that are implicitly associated with named types in existing systems Then to take these and structure a breakdown of devices into elements of form and function 4 2 1 Properties to Describe Devices The derivation of properties is accomplished by consulting a spectrum of sources relevant to building a description of what devices are and what they do i human computer interaction including virtual environments ii interconnect specifications amp platform configuration code iii operating system frameworks for device driver code development and iv device datasheets from the manufacturer Some of these sources mention properties associated with a device type whilst others define qualities without such references We organise the discussion which follows according to the categories these properties describe e characterising interaction at the user interface e physicality of devices e concurrency of access e operational control of and by device elements e non functional aspects of device operation e finer grained description of a whole device Once articulated these properties will be hierarchically related to construct an taxonomy In a later section the taxonomy will be used as a basis for describing devices 4 2 2 Interaction at the User Interface Human Computer Interaction HCI research has paid considerable attention to interaction at the interface in pursuit of raising u
27. ug us efum inpit A term classification matched value uq us enum external HEHHEHE HHHH HHHH HHHH HHHH EEE EEE ETE EE ETE EE ETE T PEPE t Ett checking have an acceptable RQGroup match comparing match factors is 40 gt 42 us enum input gous Shun external enum input q us enum external zz gt gt gt gt gt gt gt try another DGroup dgroup23 from Device green_2 us224_1 FHEHELEFELEPETEP ETE ETT E EET ttt ttt ttt HHHH gt checking availability of Registration Unit analog_audio_stream_out A term operate matched value uq us enum required M C SC term approach 175 M C SC term control A term direction matched value uq us enum unidirectional A term logical changels matched value syston integer lt 4 2 A term signal_format matched value uq us enum digital A term model matched value fug us enum stream accept submatch match factor checi 4 M C SC term Link A term compression matched value ug us enum uncompressed A term data_format matched value uq us enum pcm_audio accept submatch match factor check 6 gt 5 M C SC term channel M C SC term primitives accept submatch match factor check 12 gt 9 M C SC term comminications_link A term principal matched value uq us enum adjust M C SC term role C SC term task A term principal matched value uq us enum adjust C term role C term task A term p
28. value sampling_rate frequency kilohertz enum 32 44 1 48 data_channels system integer enum 1 2 bit_resolution system bit enum 8 16 rote 1 1 11 principal ug us enum convert electrical_interface module2 characteristics i electrical data_format ugq us enum analog mechanical_structure structures 1 1 0 cabling uq us enum false classification uq us enum external connector uq us enum mini_stereo_socket signal_lines system integer 3 direction ug us enum output link ug us enum port communications_link module3 primitives 1 channel 1 1 channel_name compression uq us enum uncompressed data_format uq us enum pcm_audio data_width system bits enum 8 16 data_rate system hertz enum 32000 44100 48000 channel 01 channel_name uq us enum left link 1 1 1 direction uq us enum unidirectional logical_channels system integer enum 1 2 signal_format uq us enum digital acknowledgement uq us enum no_ack model uq us enum stream link_name ug us enum linear PCM audio out
29. 2007 Tascam US 428 USB Digital Audio Workstation Controller user manual v3 TEAC Montebello CA USA TEAC Corporation 2007 Tascam US 224 USB Digital Audio Workstation Controller user manual D000640100A TEAC Montebello CA USA Texas Instruments Inc 1999 TUSB3200 USB Streaming Controller Data Manual datasheet SLAS240 TI Inc Texas Instruments Inc 2003 TSB43AB23 Firewire 1394a OHCI PHY Link Layer Controller Data Manual datasheet SLLS450A TI Inc Dallas TX USA 192 Texas Instruments Inc 2007 PCM2900 Stereo Audio Codec With USB Interface datasheet SLES035C Burr Brown Products Thompson A amp Taylor B N 2008 Guide for the Use of the International System of Units 811 NIST Special Publication Unicode Consortium 2000 The Unicode Standard 3 0 ed Addison Wesley ISBN 0 201 61633 5 Unified EFI Forum 2009 Unified Extensible Firmware Interface UEFI Specification specification v2 3A UEFI UPnP Forum 2008 UPnP Device Architecture specification v1 1 UPnP Forum 2008 UPnP AV Architecture specification v1 1 USAR Systems 1997 HulaPoint Ergonomic Mouse PS2 RS232 Encoder HulaCoder UR7HCDMP datasheet DOC7 DMP DS 101 USAR New York NY USA USB Implementors Forum 2000 Open Universal Serial Bus Driver Interface OpenUSBD I specification rev 1 0 Compaq USB Implementors Forum 2006 USB Device Class Definition for Audio Devices specification v2 0
30. 70 Therefore to ensure types can be shared between independent systems we shall adopt a common type dictionary Our i o taxonomy will become a language of input output for the distributed system It is suitable by virtue of its derivation being empirically grounded and sufficient because it has been drawn from a wide range of devices There is the additional challenge of versioning to be overcome That is reference must be made to the same or compatible versions of a type dictionary to define a device and formulate a request Szyperski 2003 Our type dictionary is appreciably more stable by virtue of what the structural terms represent The taxonomy is about actual descriptions of form and function and not arbitrarily created When comparing description verses naming of devices we are suggesting that the former requires far less in the way of changes over time and is better equipped to endure We assume the export of additional type definitions is not permitted and that the distributed system is set up to have foreknowledge of the shared type dictionary 4 4 2 Describing a Device To be in a position to structurally type a device requires defining what we are capturing by a device description This is about deciding what is being represented by them We examine how to go about logically accounting for a device before elaborating upon 98 functionality represented by task element modules Device typing is finalised by sectioning a larger desc
31. 8 other figure 3 3 sphere of device responsibility example Once all of the devices in the example above have been enumerated and assigned to a system then an indicative expression of them as Prolog programming language facts is as follows device computer system device bridge upstream bridge system responsible device cs1 d1 bridge processing_module self device cs1 d2 device d1 other device cs1 d3 device d1 self device cs1 d4 bridge d1 self device cs1 d5 device d1 self device cs1 d6 device d4 self device cs1 d7 device d4 other device cs1 d8 device d4 other The role of a bridge to further interconnects is indicated as are those devices on shared interconnects assigned to other systems These database entries for each computer system are adjusted dynamically as devices connect or disconnect Connections to other systems dynamic Building on the account of devices a record of other systems linked to that computer system is needed The linkage between device and computer system is also an integral part to establishing distributed communication It is through these devices that communication between processors must be physically routed An indication is provided of those adjacent but we avoid an expanded awareness of the communication paths beyond immediate links Establishing those systems which are adjacent is achieved by extending device enumeration on shared intercon
32. A term compression matched value uq us enum uncompressed A term data_format matched value uq us enum pcm_audio accept submatch match factor check 6 gt 5 M C SC term channel M C SC term primitives accept submatch match factor check 12 gt 9 M C SC term communications Link pr gghecking availability of Registration Unit analog audio_stream_out available A term configure matched value uq us enum required M C SC term approach M C SC term control A term data format matched value ug us enum digital A term signal_mute matched value system boolean true M C SC term function A term principal matched value uq us enum adjust M C SC term role M C SC term task A term configure matched value uq us enum required A term operate matched value uq us enum required M C SC term approach M C SC term control accept submatch match factor check 14 gt 10 M C SC term task element A term signal_ended matched value uq us enum unbalanced A term data_format matched value ug us enum analog A term conn ction_establish matched valu ud us enum hot_pLuggable accept submatch match factor check 4 gt 2 M C SC term electrical M C SC term characteristics A term width matched value Clength mm 8 37 M C SC term physical_dimensions M C SC term physical_manifestation A term connector matched value uq us enum
33. A term connection establish matched value ug us enum hot_pLuggable accept submatch match factor check 3 gt 2 M C SC term electrical M C SC term characteristics A term direction matched value fuq us enum input A term classification matched value L q us enum external A term direction matched value uq ug enum input A term classification matched value q us enum external A term signal_ended matched value uq us enum unbalanced A term data_format matched value geas enum analog A term conn ction_establish matched valu ud us enum hot_pLuggable accept submatch match factor check 4 gt 2 M C SC term electrical M C SC term characteristics A term direction matched value uq us enum input ternal J a M C MAC JJ A term classification matched value ug us enum external A term direction matched value uq us enum Linp t A term classification matched value uq us enum external HEHHEHE HHHH HHHH FEET EEE ET HHH HHHHHHHHHHHHHHHHHHHHHH H H HH checking have an acceptable RQGroup match comparing match factors is 40 gt 42 164 gt gt gt gt gt gt gt try another DGroup dgroup23 from Device green_2 us224_1 FETE EEE ETT EE EEE ETE EEE EE EE EEE EEE EEE EEE EEE EEE EEE EEE EEE EEE EEE peghesking availability of Registration Unit analog audio_strean_out A term operate matched value uq us enum required SC term approach SC term con
34. DCIH DCInterface 5 2 3 Match Parameters Motivation Another of our aims is to provide the requester with the option to automatically calibrate logical control of a device This not only reduces the burden on the requester to be aware of precise configuration details it improves reliability by backing the configuration of access with negotiated data parameters Identifying relevant parameters in a structural description is a straightforward task given that quantification of leaf level terms underpins a successful request anyway It is merely a matter of selecting those relevant to control Illustrative example An illustration of the utility in using parameters is a request for an audio codec that describes the module responsible for converting digital audio to an analog signal By virtue of having to describe the signal conversion task the requester has already articulated the control parameters sampling rate data channels bit resolution The correspondence recorded with the device could be used to automatically define the boundaries for operation without further querying prior or during device operation Technicals Match parameters are indicated by leaf level annotations of a structural description The requester specifies which are relevant parameters for control of a device During the match process once a leaf term and its quantitative correspondence have been determined they and the annotation are added to the results 12
35. Device e device resource allocation happens amp match transaction is recorded in database for Outlet outletl Active Request Alternative Request Alternative List composite_rq1 100 composite_rq2 50 gt gt gt try another Request Alternative composite_rql at priority 100 with Request list rq next Request rq1 with RQGroup list rqgroup1 gt gt gt gt gt try another Device green_2 us224_1 next RQGroup rqgroup1 gt gt gt gt gt gt gt try another DGroup dgroup21 from Device green_2 us224_1 FHEHELEEELE TELE PETE ETE t ttt ttt ttt ttt ttt ttttttttttttt t FHEPETE LET HHHH HHHH HHHH HHHH EEE EE ETE EE ETE TEEPE TEEPE EEE checking have an acceptable RQGroup match comparing match factors is gt 23 gt gt gt gt gt gt gt try another DGroup dgroup22 from Device green_2 us224_1 FHEHHLETHLE PTET tt tt ttt ttt ttt ttt ttt ttt ttt ttt ttt checking availability of Registration Unit analog_audio_stream_in available A term sampling_rate matched value frequency hertz 44100 A term data format matched value ug us enum Canalog A term conn ction_establish matched value ug us enum hot_pluggable accept submatch match factor check 3 gt 2 M C SC term electrical M C SC term characteristics A term classification matched value ug us enum externa A term Classification matched value ug us enum external A term data_format matched value ug us enum tana
36. Griffin_Technology 2010 The process of deriving the structure detailed below is included in the appendices The facts listed below illustrate how we accomplish building a device description by using DGroups to structure association As a guide the modules TE EI CL UI comprising this device divide into the following DGroups 1 G General 102 2 TE DAC TE Mute TE Volume CL AnalogOut EI AudioOut CL DigitalOut 3 TE ADC TE Gain UI MicLineSwitch CL AnalogIn EI AudioIn CL DigitalIn deviceStructure imic2 dg deviceGroup general ea 01 0 1 deviceGroup imic2 dgroup2 task_element HH task 1 IN function l data_ n signal_mute rote 1 1 i I principal i task_element task 1 1 1 function D data_format signal_attenuat role 1 1 1 principal rO ll J electrical_interface imic2 dgroup1 roup1 dgroup2 dgroup3 l ll uq us enum digitall system boolean true ug us enum adjust 1s ll ug us enum analog ion ratio decibel_volt between 10 6 ug us enum adjust 11 01 characteristics electrical LA l 1 01 0 1 011 data_format uq us enum analog Lie sence structure ae structures
37. Match X MF Y ASPECTS loop through list amp try terms at current level RQGH RQTermName ODI RQMF RQAV use request term name with univ operator to check for existence of device term NewMatchTerm RQTermName OldTerm NewTerm L1 NewMatchTerm aspect NewTerm DeviceAV aspectValueCheck RQAV DeviceAV MatchAV L2 1 CUT add sub match acceptance measure as per request annotations then add to results deviceElements NewTerm DS addAspectMF RQMF MF NewMF L3 NewMatch RQTermName ODI DS MatchAV Match L4 WalkRQGroup Requester Device OldTerm RQGT NewMatch X NewMF Y WalLkRQGroup Requester Device OldTerm _ RQGT Match X MF Y Aspects iterate on no result for current term WalLkRQGroup Requester Device OldTerm RQGT Match X MF Y Matching RQGroup helper goals checkSubMatch _ _ _ failure where no submatch CUT fail checkSubMatch _ SubMatchMF RQMF AcceptMF RQMF success on acceptance measure reaching interim requirement CUT SubMatchMF gt AcceptMF checkSubMatch _ _ success where no annotation present Notes checkRegistrationUnitAvail aspectValueCheck amp executeMatchConditions goals were all described earlier in the process enhancements section 138 5 4 Search Optimisation The inference engine adopts a basic depth first strategy to systematically explore the search space This approach to seeking correspond
38. Once results have been derived it is responsible for applying them to enable access to a device By the IO Composition service being linked through from IO Configuration and IO_Discovery this changes how connection events are handled Composition becomes not only a computer system s but also the distributed system s response to a device connecting In turn this enables remote access to be established as the end result and not just preparing a device for operation 6 1 2 Taxonomy and Structural Description of Devices Devices are described in terms that are based upon a minimal abstraction of physical hardware Our design not only defines an ontology for describing devices but also to define requests It consists of an i o taxonomy and a structural description that uses terms from the taxonomy to describe rather than name the type of device An i o taxonomy is built to structurally type devices It is derived from our investigation of properties describing their form and function The work examined cuts across research industry standardisation efforts and device specifications A language of input output is captured that describes elements from a broad spectrum of devices These elements of a device are formed into a cohesive whole through a structural definition Descriptions are refined by establishing the capacity to associate elements together according to the task they perform or their location within an interface A flexible formulat
39. RQGroup i determine device term then check for its existence in database ii for branch terms recursively try same steps using sub structure beneath term iii where annotated perform checks to accept sub match using process enhancements iv add term sub match branches only plus annotations to results before selecting next term at the same level 3 where annotated check result reaches acceptance measure 4 failure forces the search process to try another DGroup A range of process enhancements are possible and are discussed in a later section We examine the structure of results before returning to deal with uncertainty in those results and outlining how a device term is determined then checked for its existence 5 1 2 Generating the Results Matching styled for a distributed system Our intention is to structure match results for use in a distributed context where application of a match is likely to be remote from the other participants and from the computer system where matching was conducted This requires results to be expressed suitably for communication back to the participants possibly on separate systems where device resource availability and requester configuration can occur Results are intended to be retained past their application for later reference when either a better match is found or the match must be removed With results expressed in the right manner they can be referenced to apply or remove a match and the op
40. Sedivy J Z Smith T F amp Izadi S 2002 Challenge Recombinant Computing and the Speakeasy Approach In Proceedings of the 8th ACM International Conference on Mobile Computing and Networking Mobicom 2002 DOI 10 1145 570645 570680 pp 279 286 Electronic House 2011 Apple of Their Eye Apple based control system and an electronic British butler Electronic House Los Angeles CA USA viewed May 2011 lt http www electronichouse com article apple_of_their_eye gt Ellis S R 1994 What Are Virtual Environments JEEE Computer Graphics and Applications vol 14 1 DOI 10 1109 38 250914 pp 17 22 European Computer Manufacturers Association 1992 User Interface Taxonomy technical report TR 61 ECMA Fineberg M L 1995 A Comprehensive Taxonomy of Human Behaviors for Synthetic Forces technical paper ISA P 3155 Institute for Defense Analysis Alexandria VA USA Firmworks 2005 Open Firmware Features Firmworks Mountain View CA USA viewed December 2013 lt http www firmworks com www features htm gt Fleishman E A Quaintance M K amp Broedling L A 1984 Taxonomies of human performance the description of human tasks Academic Press Orlando FL USA ISBN 0 12 260450 4 Foley J D Wallace V L amp Chan P 1984 The Human Factors of Computer Graphics Interaction Techniques JEEE Computer Graphics and Applications vol 4 11 pp 13 48 Fuchs H amp Bishop G 1992 Research d
41. The key points where guidance is necessary are i arequester s external access point outlet may be associated with multiple alternatives ii an alternative may consist of multiple requests iii a request will typically consist of multiple RQGroups iv a structural description associated with a RQGroup will correspond unpredictably i Satisfying a requester s external access point A requester s external access point or outlet may be associated with multiple alternatives Without guidance it is possible for a search to return results that are less desirable because better alternatives could have satisfied The requirement is to ensure the most preferable alternative is matched What is needed is to rank the list of alternatives thereby allowing the requester to decide on an ordering of compromises overall ii Satisfying a Request Alternative A request alternative may consist of multiple requests Without guidance it is possible for a search to bind devices to only some requests in an unpredictable manner The requirement is to ensure every request associated with an alternative is sufficiently matched What is needed is to require every request in the list to bind to a device and be matched iii Satisfying a Request A request will typically consist of multiple RQGroups Without guidance it is possible for the search to bind DGroups from the current device to only some RQGroups in an unpredictable manner The r
42. This implies a heavy focus on virtualising rather than incorporating new devices Consequently they avoid making comparisons between the utility of devices employed and other two dimensional technologies 79 transmission figure 4 4 Performance Characteristics for Communication Channels delay bandwidth resolution dynamic range signal noise DISPLAYS Cuar arcmin pixel 8 bit scale color 25 1 20 100 msec 20 100Hz within 5 central vision 60 field contrast ratio 30 stereo overlap 30 field overlap stereoscopic 2 disparity range 120 1 100 msec 0 1 5Hz 2 arcmin pixel within central vision 0 1 6 meter single convergence disparity ratio tactile 10 100 micron vibration 200 1 5 msec 0 10kHz 1 2mm spatial resolution 8 bit RMS ratio kinesthetic force 20N DC to 1N 10Hz 64 1 P 20 msec 50 100Hz 0 1 newton 6 bits 1 10cm RMS ratio g audio 5 g sound 16 bits 40 1 g T 1 msec 20Hz 20kHz frequency 0 02 3Hz power 2 dB 60 dB RMS ratio 2 S directional sound 5 amp relative direction 1 5 C E P 20 30 1 solid E z 50 500 msec 3 6Hz absolute direction 20 30 4 pi steradians angle ration 2 R ocal synthetic speech 90 95 recognition 10 100 msec 1 5 2 words sec in 50000 word vocabulary potentially unlimited CONTROLS manipulative mice joystick pedals trackers etc 3 10Hz 0 2 joint angle 100Hz for force 1 4
43. Where a result is of a higher ranking than an existing match it must be cancelled before applying the new IO Results references record of the pre existing match to advise IO Outlets to tear down record with the requester Notification is also sent to the system s where the device s are connected that are part of the pre existing match Their IO Results support service references stored results to advise IO Resources to adjust record of resource allocation Where a pre existing match got cancelled resources became available therefore the process is re triggered and IO_Composition notified 71 72 4 Taxonomy and Structural Description of Devices In this chapter we define a logically visible means of describing devices and structuring requests for their functionality across a distributed system An taxonomy is built from an investigation of properties describing device form and function A structural description using terms from the taxonomy defines how to describe devices Formulation of requests is also outlined using the taxonomy 4 1 Overcoming Named Type Restrictions A useful starting point for our work is devising means of overcoming restrictions discussed earlier that are inherent in the use of named types This requires expanding our awareness of a device beneath that of a whole and outside of logical interfaces In particular articulating properties that are implied by reference to a named type 4 1 1 Assigning Types to Who
44. XML based for describing web services as a set of endpoints operating on messages containing either document or procedure oriented information Part of a service description is a definition for a target namespace 35 2 4 2 Problems With Device Descriptions The use of names for types Whether assigned to whole devices or just service interfaces the use of a name or code to denote the type of device functionality is a predominant approach It has the effect of establishing the granularity to treatment of a device at that level There is no variance A further consequence is an overly simplistic match algorithm Effectively matching becomes an implied step where it is a trivial aspect of discovery The only equality relation permitted when matching names is exact correspondence This is referred to as named type equivalence Connor Brown et al 1990 Past efforts be they interconnect specifications through operating system kernels or middleware have assigned a value to represent a particular type of device The use of a code provides no guidance as to the device s structure or functionality Instead properties are implied by use of the type and require that there be agreement regarding reference to a dictionary of names or types Connor 1990 Hardware independent or arbitrary abstractions At the lowest level of abstraction attempts to describe hardware rely upon interconnects to define concepts The differences between them preclude
45. a single structure An issue arose from the perspective of formulating a request for device specifics A finer granularity is needed than association with a whole device It is sufficient to describe devices by using a single structural description But asking for modules requires some guidance to indicate how they are related This emerged as a problem because searches are free to return modules as long as they come from the same device Without control over element level association there is no way to improve search quality As such it becomes necessary to organise descriptions into sub sections rather than a flat representation The concept of sub sections is not a doubling up on detailing logical connections Instead it is about establishing boundaries around significant sub sections describing these modules and indicating they are related Our analysis suggests that the sort of sectioning required has an internal aspect related to describing functionality and an exterior that accounts for form Aligning according to functionality is more specifically about identifying distinct signal paths through multiple modules For example an audio device with a headphone port has a digital to analog conversion task element associated with the electrical interface for the headphone It may also have digital or analog volume adjustment or mute task elements Without association the mute or volume adjusters from ports elsewhere on the device could also sat
46. a device s is expressed more formally as compositeRequest requester composite_rqi rq2 rq3 request requester rq2 request requester rq3 An example where multiple requests may lead to more than one device being included in the match results is audio streaming in and out A separate stream request for each would permit satisfaction spread across two devices Presenting Request Alternatives The definition of requests lacks flexibility in terms of adjusting which modules to seek when a particular combination is not available Simply expressing them as a list of requests does not provide options where satisfaction remains problematic across many devices Consider the example of an audio control surface device that has interface controls associated with four channels Where there are less than four of these devices present a request for 16 channels is going to find inadequate satisfaction We need to supply further options when the current request is inadequate An avenue to pursue would be allowing some requests to go unmatched but we will return to this shortly to discuss why that might be problematic To provide alternatives we chose to allow separate composite requests that will be checked for correspondence one after the other This grants the requester control over what compromises are acceptable when the 107 ideal device s is not present A list of composite requests is associated with an external access poin
47. all Bluetooth devices CD ROM drives including SCSI CD ROM drives hard disk drives video adapters floppy disk drive controllers floppy disk drives hard disk controllers including ATA ATAPI controllers but not SCSI amp RAID interactive input devices Dot 4 devices that control the operation of multifunction peripherals Dot4 print functions Firewire devices that support IEC 61883 protocol audio amp video streams Firewire devices that support AVC protocol device class Firewire devices that support SBP2 protocol device class Firewire host controllers connected on a PCI bus but not peripherals still image capture devices digital cameras amp scanners infrared devices all keyboards SCSI media changer devices memory devices such as flash memory cards modem devices display monitors all mice amp other kinds of pointing devices such as trackballs combo cards such as a PCMCIA modem amp netcard adapter audio amp DVD multimedia devices joystick ports amp full motion video capture intelligent multiport serial cards NDIS miniport drivers network amp or print providers network services such as redirectors amp servers NDIS protocols devices that accelerate secure socket layer SSL cryptographic processing PCMCIA amp CardBus host controllers but not peripherals serial amp parallel port devices printers CSI 1394 enumerated printers for a specific bus processor types SCSI HBAs Host Bus Adapters
48. amp disk array controllers smart card readers storage volumes as defined by the system supplied logical volume manager HALs system buses amp bridges system ACPI driver amp volume manager driver tape drives including all tape miniclass drivers USB host controllers amp USB hubs but not peripherals WindowsCE USB ActiveSync Devices Windows CE ActiveSync devices Windows SideShow all devices compatible with SideShow supported in Windows Vista amp later figure 2 13 system defined device classes provided by Windows Driver Kit Operating System Abstractions of I O Highly abstracted access to device functionality is embodied in select system libraries presented by the operating system or frameworks extending system software Oliver Shcherbakov et al 2010 Two separate examples are used to illustrate abstractions in use within current systems 32 A widespread pattern has been to reference devices as if they were a file located at a particular point in the file system namespace of an operating system Opening and closing a file is used to request access and communication is represented by reading and writing data to the same file refer to UNIX special directory dev Leffler McKusick et al 1989 The Plan 9 operating system extends the filesystem model to represent all resources including devices as files Even system interfaces are provided via special files In this way driver code interfaces are implemented as related
49. and alluded to requests being made in terms of device elements Some discussion is necessary to clarify what constitutes type equivalence between two devices This is to reinforce our departure from checking equivalence using named types and prior to introducing request formulation Distributed systems are constrained by independently deployed computer systems that are operating autonomously Sharing types between independent systems is problematic Reaching distributed agreement on device typing requires references be made to the same type dictionary or a compatible version Our stated assumption is to proceed on the basis that the distributed system has foreknowledge of a shared type dictionary in the form of the i o taxonomy To share device descriptions between systems requires extending the distributed agreement to the structures discussed in the previous section Using structural typing a question that arises is when can two devices be said to be of the same structural type and how is this demonstrated Connor states that for two types to be equivalent they must be created with the same type constructor and in an equivalent manner Connor 1990 72 The distributed system utilises a single type constructor i o taxonomy but doing so in equivalent manner needs expanding Connor provides clarification in arguing to perform structural type equivalence checking it is necessary to build representations of types which contain suff
50. another DGroup dgroup3 from Device red_1 imic2_1 HEHHEHE HHHH HHHH HHHH HHHH EEE T PETE EE ETE ETE TEE TEEPE TEP Et gt checking availability of Registration Unit audio_stream_in available A term direction matched value uq us enum analog_to_digital A term sampling_rate matched value frequency hertz 48000 A term data_channels matched value system integer 2 A term bit_resolution matched value system bit 161 accept submatch match factor check 9 gt 9 M C SC term function A term principal matched value uq us enum convert M C SC term role M C SC term task accept submatch match factor check 14 gt 14 M C SC term task_element A term direction matched value uq us enum unidirectional A term logical_channels matched value system integer 2 A term signal_format matched value uq us enum digital A term model matched value uq us enum stream accept submatch match factor check 6 gt 4 M C SC term Link A term compression matched value uq us enum uncompressed A term data_format matched value uq us enum pcm_audio accept submatch match factor check 6 gt 5 M C SC term channel M C SC term primitives accept submatch match factor check 12 gt 9 M C SC term communications_Link HEHHEHE ELE ET HHHH HHHH HHHH EEE TEETH E EET ETE TEETH TEETH checking have an acceptable RQGroup match comparing match factors is 26 gt 23 RQGroup match found with DGro
51. application This ensures clean removal of speculative results before pursuing a different search The decision to alter how structural matching proceeds arose from an acknowledgement that device descriptions are more than a static account of form and function Providing a more dynamic picture though requires altering resource availability and state assertions that were submitted for matching alongside structural descriptions In the context of an automatic search facility this presents a problem to avoid side effects when the backtracker is engaged Consequently the process requires careful placement of goals for removing then restoring assertions 5 3 4 Satisfying a RQGroup Guidance on satisfying a RQGroup determines how correspondence is derived between the structural descriptions associated with RQGroups and DGroups It also evaluates the quality of correspondence between them How did it come about Using structural descriptions to represent a request leads to issues of how to check correspondence and how to prevent the search from returning trivial matches Checking devices cannot be conducted as a straightforward traversal of both structures This is due to the possibility of less than exact correspondence A more speculative approach is required to frame the search as determining whether a particular term exists within the structure Then without a means for measuring and evaluating non null correspondence between structural descript
52. are implicitly bound to a processor undermining any flexibility gained by resolving other driver relations We are guided by virtual machine use of intermediate byte code compilation in defining a target instruction set based on a virtual processor An observation is that translation requires a one to one replacement of instructions as distinct from compilation where a single line of higher level programming language code may require multiple assembly instructions Once compiled to an intermediate assembler code then all that is required is to generate corresponding native code by translating The only wrinkle is the need to express i o access instructions in a processor independent format With an intermediate target for compilation it is possible to prepare driver code without consideration of which processor The device description is required to store the intermediate code The IO_Configuration service extracts a driver code block and makes reference to a record stored on that processing module to translate the block to code suitable for the processor The translation table for virtual processor to native instruction set is discussed below 3 3 5 Protocol Definitions Device configuration procedure for use by driver code Utilising composition as a means of establishing access to devices implies they must have been readied for participation in the process The dependency a device has necessitates drive code configuring it for operation A pro
53. bits dof discrete control range exoskeletal limb motion 200 1 10 msec reflection 10 bits dof continuous control 20N DC to 1N 10Hz RMS ratio ocal speech recognition 1001 1 2 sec 1 2 words sec lt 5 probability of misrecognition 20000 words RMS ratio Sensory modality of interaction Human Computer Interaction and Virtual Environment research describe devices in terms of the interface presented to the human user during task conduct Broadening the categories used for describing interfaces is possible through reference to the sensory dimensions of that interaction Existing systems however provide a limited perspective on what is possible To provide greater descriptive capability it is necessary to step outside of them by making reference to the human perceptual system The task of deriving a sensory model was completed in earlier work by the author on Virtual Environments and is presented in figure 4 5 Katyan 1993 32 9 Senses are referred to as those for perceiving via stimulation of sensory organs as in vision hearing touch smell and taste and indefinite body feelings as in orientation and balance These are broken down further into mutually exclusive sub categories and find application in both input and output interaction channels 80 Vision 3D Monocular Binocular Mono A Stereo Hearing son oprac Quadraphonic Environmental Noise Isolated Sounds Wetness Sensation
54. but separate data control and status files They are referenced by name and their contents accessed by read and write calls A further abstraction of devices arises at the user interface in the concept of a workstation e g Xerox Star It embodies concepts from research into aspects of human cognition The output device is a colour graphics display and input is enhanced by pointing and selecting via a mouse Johnson Roberts et al 1989 The abstractions are based on an underlying model detailed in figure 2 14 Kay 1990 197 DOING mouse enactive know where you are manipulative with icons iconic recognise compare configure concrete IMAGES windows makes Smalltalk symbolic tie together long chains of reasoning abstract SYMBOLS _ programming language figure 2 14 doing with images makes symbols model The output screen a two dimensional array of coloured pixels is abstracted by collecting groups of them together as icons or windows and even text using varying fonts Through operating system support input becomes tightly integrated with the generation of events involving control of the mouse to move a pointer displayed on the screen for selecting symbols Text generated by the keyboard is delivered to whichever requester is the currently designated candidate for receiving communication by the user interface Extending Abstractions to the Distributed Context The projects chosen extend an abstraction of a single computer syste
55. c ept cubeten Match factor check 14 gt 10 SC term task element A term signal_ended matched value uq us enum unbalanced A term data_format matched value uq us enum analog A term connection_establish matched value uq us enum hot_pluggable accept submatch match factor check 4 gt 2 EC SC ctrical CLSC term characteristics A term width matched value length mm 8 3 C SC term physical_dimensions C SC term physical_manifestation A term connector matched value _fug us enum rca_connector rca_connector A term Classification matched value ug us enum external A term device boundary matched value syst m bodlean true C SC term relation C SC term Logical_structure A term connector matched value _fug us enum rca_connector rca_connector A term classification matched va L q us enum external A term device_boundary matched value syst m boolean true I C SC term relation C SC term Logical_structure A term width matched value length nm 8 31 I C SC term physical_dimensions C SC term physical_manifestation A term connector matched value _ ug us enum rca_connector rca_connector A term classification matched va L q us enum fexternal A term device boundary matched value syst m boolean true C SC term relation C SC term Logical_structure A term connector matched value _fug us enum rca_connectorrca_connector A term Classificati
56. complete stages The drawback with requiring intervention is that the participants must be aware of semantics Reliability A separation of composition from the flow of events on a computer system was observed in the context of discovery The consequences of distributing the process have largely been ignored and allowances are not made for dynamic configuration There is a failure to acknowledge that when disconnections happen compositional readjustment is required to rectify broken communications links As such it is difficult for existing systems to approach the reliability of the process being conducted on a single computer system There is an implicit acknowledgement that faults present a problem for maintaining access in a distributed context In resorting to the use of timeouts to detect them existing systems are not emphasizing responsiveness As such linkage between composition and the time of the event is absent Robustness is not a design priority Fault recovery during matching involves re transmission of messages and only once their validity expires Typically the absence of a response is interpreted as failure to participate when it may be due to distributed faults Reliability to communication links in existing systems is dependent upon such measures being present in the underlying networking protocols Lastly interrupting the match process elicits a lazy response through the use of timeouts meaning services eventually realise a pr
57. core of each computer system and form an integral part of a processing module Furthermore a persistent resource consisting of a table detailing virtual processor to native instruction set translation must also be embedded with the core to ensure driver code can be readied Define kernel interface for driver code use Despite driver code deploying separately it must be tailored to a particular operating system Awareness of semantics and syntax is required for access to kernel services to provision system resources for the driver not the device This coupled with the kernel dictating the structure of code creates a tight binding and consequently a dependent relation Efforts focussed on improving problems of operating system stability have taken existing drivers and isolated them from the rest of the kernel Whilst this may improve system reliability it does not alleviate any dependencies Guidance on how to accomplish their removal comes from the Device Driver Environment permitting Linux operating system drivers to execute under the L4 kernel Helmuth 2003 As discussed earlier they provide a clear indication of the full range of services required to encapsulate a driver We require standardising the kernel interface referenced by driver code to grant them independence from operating systems Kernel code running on any processing module need only implement the specified interfaces to handle compliant drivers 58 3 4 IO Composition Serv
58. dgroup2 from Device red_1 imic2_1 adding match for RQGroup rqgroup4 to match list for Request rq5 apply match with Device red_1 imic2_1 MODE apply Request Group rqgroup4 Device Group dgroup2 registration units audio_stream_out updated gt unavailable state update term bit_resolution maps gt state dac_resolution new value system bit 16 amp retained value system bit 16 state update term data_channels maps gt state dac_channels new value system integer 2 amp retained value system integer 2 state update term sampling_rate maps gt state dac_sample_rate new value frequency hertz 48000 amp retained value frequency kilohertz 44 1 completed applying RQGroup match to Device to constrain resource availability gt completed matching entire RQGroup list for Request rq5 X checking have derived a match for Request rq5 adding match for Request rq5 to match list for Request Alternative composite_rq3 gt completed matching entire Request List for Request Alternative composite_rq3 X checking have derived a match for Request Alternative composite_rq3 MATCH RESULT match found found match for Request Alternative at priority exceeding 25 for Outlet with pre existing match cancelling existing match for Request Alternative composite_rq4 involving RQList rq4 cancelling existing match for Request rq4 involving Request Group List rqgroup3 cancelling existing match f
59. expression in specific units with the boundary as a precise value or as needing to meet or exceed some threshold Technicals Structural matching at the lowest level involves matching terms Aspects then checking the extent of value correspondence Aspect Value This quantitative measure is expressed in terms of four properties e quantity as a standard measurement classification e g length 124 e symbol as a unit of measurement within a classification e g m as metres e range as the value range symbol e g gt as greater than e value as a list of values denoting discrete or boundary values e g 10 20 to denote between 10 20 During traversal determining value correspondence is a requirement for leaf term Aspect inclusion in the match results Failure occurs if the quantities do not agree or the range of values have no overlap Implementation specifics The implementation utilises the same structure to express all values for example a request for an audio codec capable of a sampling _rate exceeding 44 1KHz is expressed as sampling_rate frequency hertz gt 44100 Then amongst the device facts for an audio device the codec capabilities are recorded as aspect devicel_dgroup2_te3_task_function_sampling_rate frequency kilohertz enum 32 44 1 48 Goal expression The determination of value correspondence goal is detailed below aspectValueCheck RQQ RQS RQR RQV DQ DS D
60. figure A 4 M Audio Audiophile device structure 152 A 1 3 Tascam US 224 The Tascam US 224 device is classified as an audio control surface with stereo audio codec MIDI interfaces with digital IN OUT It is described minimally in the user manual supplied with the product TEAC 2007a The device manifests as indicated in figure A 5 figure A 5 M Tascam US 224 device front and back view It consists of a processing box attaching to a computer system via the USB interconnect Externally the box has a range of buttons LEDs sliders and knobs for guiding software in controlling audio signals and there are various knobs for adjusting analog output levels directly At the rear it has a range of Audio IN and OUT ports both analog and digital plus MIDI IN OUT to which attach audio sources and destinations It requires external power source to be connected Device Description With reference to performance specifications published with the user manual a description was prepared for a specific sections related to the needs of the testing the implementation Device Structure a series of groups each comprising a range of modules group 21 general G task elements TE type control source 22 Analog to Digital Converter convert USB Control 22 ADC Mute adjust USB Control 22 ADC Gain A B adjust USB Control 23 Digital to Analog Converter convert USB Control 23 DAC Mute adjust USB Control 23 Line Out Volume adjust UI Line Out Level
61. green_2 us224_1 reversing application of group matches so far with same device aborting Request List at rq1 amp returning null match X checking have derived a match for Request rq1 gt gt gt gt gt try another Device blue_3 audiophile_1 next RQGroup rqgroup1 gt gt gt gt gt gt gt try another DGroup dgroup11 from Device blue_3 audiophile_1 FEFELEFELEE ETE EL EET EE ETE EET EET EET EET EET EET Ett ett ttt go checking availability of Registration Unit analog audio strean_out available term sampling rate matched value frequency hertz _ 48000 term data_channels matched value system integer 2 term bit_resolution matched value system bit 16 A term principal matched value ug us enum convert C term role C term task A term operate matched value uq us enum required C term approach A A A term control term direction matched value ug us enum uni directionat term logical_channels matched value system integer 2 term model matched value ug us enum stream accept submatch match factor check 4 gt 4 M C SC term Link CSC term primitives A term direction matched value ugus enum unidirectional 1 A term logical_channels matched value system integer 2 A term signal format q matched value ugus enum digital A term model matched value ug us enum stream accept submatch match factor check 6 gt 4 M C SC term Link
62. intended to be used as a framework for defining minimum functionality that must be implemented USB_Implementors_Forum 2006a Reference to a USB class implies an understanding of how to logically access particular device functionality 28 use class information in the interface descriptor Audio Communication amp CDC Control Human Interface Device HID Physical Image Printer Mass Storage Full speed hub Hub Hi speed hub with single TT Hi speed hub with multiple TTs CDC Data Smart Card Content Security Video Personal Healthcare Diagnostic Device Bluetooth Programming Interface UWB Radio Control Interface Remote NDIS Host Wire Adapter Control Data interface Device Wire Adapter Control Data interface Device Wire Adapter Isochronous interface Active Sync device Palm Sync Miscellaneous Interface Association Descriptor Wire Adapter Multifunction Peripheral programming interface Cable Based Association Framework Device Firmware Upgrade IRDA Bridge Device USB Test amp Measurement Device USB Test amp Measurement Device Wireless Controller Application Specific Vendor Specific figure 2 10 Universal Serial Bus USB Class Codes Describing Hardware Platform Configuration Code The first example of platform configuration code is Open Firmware that during system initialisation
63. interconnect accessible structures Being able to interpret a device s logical structure is a necessary prerequisite to facilitating configuration Once operational this includes knowing how to sequence control and arbitrate access to specific hardware The extent of awareness is relative to the role expected of a driver A diagrammatic representation of expanding coverage is shown in figure 2 2 14 specific driver code interconnect driver code figure 2 2 relative driver coverage of a device Coverage begins with access via a bridge to an interconnect upon which the device is attached e g access to PCI interconnect configuration space on a device It extends through to standardised interfaces exported by a device e g VGA graphics compatible structures to a specific device instance e g specific graphics accelerator At a minimum an interconnect bridge driver is aware of logical structures and access mechanisms specific to that interconnect This means it is able to access connected devices The dependency relation concerns extraction of an identification block during configuration An example is driver code for a PCI to Firewire bridge which can introspect devices on the Firewire interconnect to discover their identity refer to Texas Instruments TSB43AB23 based PCI adapter card Texas Instruments 2003 Becoming more specific a standardised interface driver includes interconnect specified structures but extends compreh
64. is required to prepare a device for operation and to ensure their functionality is made accessible Because devices require system resources to function we cannot assume configuration occurs without incident Further they lack autonomy due to needing external intervention to arbitrate access to them control their operation and be configured Uncovering those system relations which constrain device preparation becomes critical in a context where they connect dynamically It also has relevance beyond them becoming operational Configuration is how they are made ready to participate in composition across a distributed system Scope of possibilities Because constraints have the potential to prevent devices being configured investigating their impact is worthwhile When they arise is not limited a device connecting to a system They emerge during development as constraints are placed on the design of devices and driver code The value in articulating them is to explicitly account for factors that affect the process Our focus is to investigate relations between elements on a computer system This includes identifying the provider of resources required by a device and which system entity is arbitrating or controlling them At the same time to articulate the constraints present and the way existing systems have attempted to handle dependencies 2 3 1 Articulating System Dependencies Device Related System Elements Whether permanently attached or
65. knowledge base specific to devices and requests 2 an inference engine that knows how to use this knowledge to find correspondence amp 3 an understanding of how services are to communicate knowledge within the distributed system 5 1 The Match Process Satisfaction of requests is pursued by the inference engine using problem specific information to guide the search along more promising directions Requests are presented as a series of options each describing variants of sought after form and functionality and not necessarily whole devices A consequence of this approach is that the search for correspondence requires careful management In this section we outline the steps taken to satisfy a request look at the structure of the match results and discuss dealing with uncertainty at points in the process Later sections focus on enhancements to the process providing search guidance as well as optimising the search 5 1 1 Systematically Satisfying A Request Composition across a distributed system At a distributed level composition is initiated by a change in the availability of device resources However it is only conducted when checks reveal there is a requester with an unfulfilled external logical access point Once the match service has been triggered the steps undertaken are 1 submit request alternatives associated with a requester s external access point or outlet to the computer system responsible for matching 2 dete
66. mid level goal detailed below and helper goals stated thereafter attemptMatchUsingRQGroupList _ _ _ RQ _ MatchList MatchList success return a non null list of matches for a request attemptMatchUsingRQGroupList Requester Outlet CompRQ RQ RQGH RQGT Device MatchList X group to try must be associated with the current Device device _ Device DSpec _ deviceStructure DSpec DeviceGroupList member DGroup DeviceGroupList with select Device amp group list from current request try to satisfy sub goal matchRQGroupWithDGroup Requester RQGH Device DGroup GMatch GMF apply match to Device RQGMatch Requester Outlet CompRQ RQ RQGH Device DGroup GMF GMatch applyMatchWithDevice apply RQGMatch 1 CUT add match to list of matched groups attemptMatchUsingRQGroupList Requester Outlet CompRQ RQ RQGT Device RQGMatch MatchList X attemptMatchUsingRQGroupList _ _ _ RQ RQGH _ Device MatchList where unable to satisfy any group return a null match for request remove matches applied to Device for groups tried earlier removeDMatchApply0fGroups MatchList L CUT Matching request helper goals removeDMatchApplyOfGroups removeDMatchApply0fGroups Match MList applyMatchWithDevice remove Match 1_1_1_r_ Device _ _ _ Match retractall state Device _ _ shadowed 134 removeDMatchApply0fGroups MList applyMatchWithDevice _ applyMatchWithDevic
67. minimum input required to support Consoleln device Simple Text Output control text based output devices graphical console UGA Draw provides basic abstraction to set video modes amp copy pixels to from graphics controller s frame buffer UGA I O provides basic abstraction to send I O requests to graphics device amp any of its children pointer console Simple Pointer provides services that allow information about pointer device to be retrieved boot from disk Block I O provides control over block devices Disk I O used to abstract Block I O interfaces Simple File System provides a minimal interface for file type access to device Unicode Collation used to perform case insensitive comparisons of Unicode strings plus partition support for MBR GPT EI Torito boot from network UNDI interface Simple Network provides services to initialize a network interface transmit receive packets amp close network interface PXE Base Code protocol used to control Preboot Execution Environment PXE specification compatible devices plus Boot Integrity Services to validate boot image byte stream e g UART Serial I O used to communicate with any type of character based Device PCI bus support PCI Root Bridge I O provides basic Memory I O PCI configuration amp DMA interfaces used to abstract accesses to PCI controllers behind a PCI Root Bridge Controller PCI I O provides basic Memory I O PCI configuration amp DMA interfaces to access a PCI contro
68. operation e g on off 81 4 2 3 Physicality of Devices Devices are manifest in the physical environment Describing factors related to physical form would provide the requester with the ability to specify particulars of relevance to task conduct in the environment and have them be considered during composition Further properties concern mechanical structure electrical interfaces connectors through to detailing device power requirements In particular cases synchronous operation implies timing concerns Work toward discerning properties of the physical is covered by interconnect specifications as determinants of physical connections and power management Exemplars illustrate the range of properties contained within Physical connections In an environment where devices are developed separately and deployed independently to a computer system there must exist means of ensuring that device attachment happens without incident Presently these requirements find mention in reference material used to engineer devices and accompanying product manuals In external documentation is where the physical connection is stipulated including the dimensions description of physical materials and mechanical properties The specification for the interconnect used for the connection becomes a central repository of details referenced during development of a device refer to adapter card connectors in mechanical chapter of PCI interconnect specification PCI SIG
69. others have aspects where removal or alleviation would improve flexibility A drawing out of those aspects requiring attention appears below for device then driver code dependencies e device dependencies driver code fundamental kernel code inherent task dependency to ensure system resource allocation alleviation involves independent structure to a device specifying system resource requirements amp stating requirement for use of DMA platform inherent task dependency to ensure system resource allocation configuration _ alleviation involves independent structure to a device specifying code system resource requirements interconnect inherent aspect to device design specification partial alleviation involves independent structure to device description processor isolated to processor interconnect attachment e driver code dependencies kernel code removal required to ensure configuration is operating system kernel independent platform n a configuration code interconnect inherent aspect to device design specification processor removal required to ensure configuration is processor independent Previous attempts to avoid an unusable device when configuration encounters unmet dependencies are characterised by tackling them in isolation Further they fail to remove the dependency in question instead focusing on reducing the likelihood of problems A representative sample of these ef
70. overcome these restrictions Where expression of functionality is highly abstracted composition becomes a matter of matching requests for arbitrary software concepts This is an important observation because devices are special They have a physicality that defines their form and function Describing them is not arbitrary it is based on physical world concepts Therefore seeking hardware independence defeats the benefits to considering devices in the first place Our proposal is to avoid abstracting away from the concrete Instead to adopt a minimal hardware dependent abstraction Finer grained requests are achievable by expanding awareness of what constitutes a device outside of logical access concerns Benefits to removal and usefulness to composition We are proposing requests targeted at specific functionality but without requiring them to be abstracted away from hardware This provides a middle ground that breaks the requirement for requesters to be aware of arbitrary names for interfaces The advantage is to separate typing from being associated with logical access We are advocating coherence by requests being made for functionality to then be granted access to related interfaces Rather than having to identify and match separate interfaces The usefulness would come from the flexibility this affords requests 4 1 3 Implied Device Properties Overview of the restriction Consideration of form and function during composition is simply not p
71. points explain why alternatives are needed Absence of contextual awareness An important consequence of the choice of interconnect is how locality is treated By locality we mean denoting where in the physical environment a device is operating or a logical identifier on an interconnect for communication purposes Proximity on the other hand is a reference to nearness with respect to locality Location is handled in a similar manner across interconnects assigning logical identifiers to successive devices e g Firewire IEEE802 USB This affords a transparency to where the device is physically and represents a straightforward way of connecting computer systems and enabling communication between them Consequently application of transparency extends to the building of middleware Saha and Mukherjee 2003 A tension exists in circumstances where context awareness is required a factor of importance in dynamic distributed systems that prioritise physical integration The problem of linking the physical to the logical is exemplified by the CoolTown project Kindberg and Barton 2001 Physical proximity to tags or beacons are used across the distributed context to facilitate discovery A code is obtained via a sensing mechanism and converted to a location independent identifier or name for the resource URN This in turn is resolved into a network locator URL for access to a webpage located on the Internet 10 Difficulties arise when att
72. remaining to be configured on interconnects attached to a particular processor Through traversal of the connection paths a sphere of controlled devices is built around a core This data structure serves as a record of the physical links between devices and provides other services with a means of mapping logical links through to physical paths Determine where composition is to be conducted To facilitate distributed access to devices composition must cross system boundaries This requires a protocol for determining upon which computer system the process will be conducted Each system has sole responsibility for managing its sphere of devices and those software entities requesting device functionality Distributing composition necessitates dealing with the dynamic nature of the context where the systems present are undergoing continual adjustment Our approach is to ensure any computer system is capable of performing matching even when isolated Negotiations between multiple systems over assignment simply build on this basis To permit matching beyond a single system necessitates formation of a cluster within which the process is to occur We adopt a centralised allocation of device resources within the cluster and ensure a unified process by conduct at a single location The determination of the systems comprising a cluster and which is to conduct matching involves a collective assessment amongst those in proximity Qualities of import may inclu
73. required In general they must be written to understand the type of thing with which they will interact including the details of communication as well as semantic knowledge such as when and how to communicate All Speakeasy devices as services implement a number of interfaces that fall into the following categories plus an indication of what functionality e Data transfer how do entities exchange information with one another e Collection how are entities on the network grouped for purposes of discovery amp aggregation e Metadata how do entities on the network reveal and use descriptive contextual information about themselves e Control how do entities allow users and other entities to effect change in them Web Services represent a range of specifications for a basic framework to support software components exporting functionality that can be discovered and accessed over a network especially the Internet Microsoft 2005 Dong Hussain et al 2013 Although a device is referred to as an apparatus through which a user can perceive and interact with the Web it is a provider of services These are defined by Devices Profile for Web Services DPWS Microsoft 2006 DPWS pulls together a core subset of the specifications to define a minimal set of constraints for implementing secure Web services It also builds on Web Services Description Language WSDL Weerawarana Chinnici et al 2002 This is a structured format
74. seeks to identify and ready select devices for operation EEE 1994 Open_Firmware_ Working Group 1996 Apple 2000 Firmworks 2005 It embodies a conception of what types constitute a particular system according to the following codes Block amp Byte Network Serial Display amp Memory Mapped Bus Within these basic types abstract interfaces to expected functionality are specified On the other hand Intel Architecture systems are covered by a series of platform configuration specifications refer to EFI ACPI SMBIOS amp PXE Intel 1999 Intel 2002b DMTF 2004 Hewlett Packard Intel Corporation et al 2009 Unified EFI Forum 2009 The principle architectural standard Extensible Firmware Interface EFI distinguishes hardware as a set of processors and core components These may produce one or more interconnects attached directly to the processors which may contain further interconnects and or device nodes arranged in a hierarchical manner A software execution environment is defined expressed as a driver model and a series of protocol interfaces intended to persist beyond the boot process Intel 2002b Pierce 2003 Unified EFI Forum 2009 An illustration of the scope and granularity of device references is presented in figure 2 11 Platform elements are denoted by codes where an understanding of their functionality is assumed by their use 29 Platform Elements Protocol s Protocol Interface console Simple Input defines
75. that by necessity require access to hardware has given rise to problems for kernel stability where they are granted special privileges With origins as i o control code for an operating system drivers retain their role as part of the kernel This means they are granted privileged execution mode whereas application code is protected from interference and unable to do the same to other software This is an implicit acknowledgement of the tangled nature of interaction between drivers and the kernel The consequences of this are demonstrated in research into where operating system errors originate They found a higher degree of unreliability to driver code in comparison to the rest of the kernel Chou Yang et al 2001 There has been some work looking to articulate the dimensions of what the kernel is to provision and the relationship between it and the device The Singularity operating system defines drivers as components utilising interface contracts to specify the dimensions of interaction with external entities Specifying these in the form of a protocol definitions accompanying the driver code permits verification at development time Hunt and Larus 2004 Hunt and Larus 2007 Some recent efforts illustrate the difficulty in tackling removal of privileges from driver execution In Nexus an attempt was made to 21 experiment with execution mode changes by elevating drivers to application code level This was combined with formal verification
76. the friendly fun evenings spent at your place discussing research then enjoying fine wine and food Peter the enthusiastic researcher astounding programmer and most of all a friend We met as both of us encountered the write up stage and through our discussions a common interest in Operating Systems emerged I look forward to the years ahead and the chance to discuss how we might shape the discipline Significant friends from my journey are NV Jonno Richard and Thoran I would not have been able to figure out the important issues had each of you not been so enthusiastic about chatting showing insight and encouraging me to keep gophering away Michael B the mathematician for his encouragement to stick at trying to explain the concept that I saw outside the cave and not let wild horses drag me away from the project no matter how hard it becomes to make progress My sister Shello who acknowledged the sacrifices required of long term study and the extreme financial struggle to keep the show going You made a difference when there was no one else I was able to turn to for support My mother and father who have been there to provide support and encourage me to keep going when I doubted my strength to continue Finally to my father who such a long time ago impressed me with a grand typed manuscript that was his PhD thesis You inspired me to want to make my own contribution to the world of intellectual enquiry vi Statement of Originali
77. their use outside of the interconnect concerned At another level the use of hardware independent abstractions to describe device functionality is combined with named types to refer to them This is problematic as it provides no guide to underlying physical properties Furthermore composition is faced with matching the arbitrary term or having to reject it altogether There is no in between and no further options are available From a whole device down to service interfaces the focus of abstractions is centered around functional aspects Even at a finer granularity there is an absence of reference to non functional aspects Consequently composition is unable to factor in consideration of device properties beyond a name denoting implied functionality 2 4 3 The Distributed Match Process This section looks at when where and how composition happens plus access establishment across a distributed system It builds on the who and what of the process that we examined in the previous section Process of Composition When Composition occurs as a result of events happening across the distributed system When the process gets conducted is a matter of whether changes to requesters or devices act as triggers and the extent of user involvement in mediation or simply automatic DLNA delivers media interoperability across a home network and utilises the concept of devices device services and control points as requesters Allegro Software 2006
78. types then matching considering criteria such as service guarantees is not an option Furthermore if the requester has no knowledge of a type then there is little value in context awareness or having a responsive system There is a need for a more robust approach Along with addressing the issues raised one that builds the trends into their approach as if they were a series of challenges Context of Computer System Design and Construction Further complicating the trends is the context within which computer systems are designed and constructed We touched on these factors in terms of device configuration They can be summarised as i system elements are being allowed to evolve independently and deploy separately to each other 11 computer systems are defined according to a system platform design The impact of both is to impart greater brittleness to distributed systems Although devices outside of a system platform are still discoverable it makes configuration more likely to fail This is due to placing boundaries on the universe of known devices for a platform and allowing separate deployment of elements that have dependencies upon each other As such the implications of trends happening within this context are that they aggravate the shortcomings further 41 2 5 2 Arriving at the Technical Requirements We introduced a model of the process for establishing access to devices It was used as a framework for examining existing work in
79. value uq us enum required A term operate matched value uq us eum Pequired M C SC term approach M C SC term control A term data format matched value fug us enun digital A term signal_mute matched value system boolean true M C SC term function A term principal matched value ug us enum adjust role M C SC term task A term configure matched value uq us enum required A term operate matched value uq us enum required M C SC term approach M C 5C Seespt SUMTER match factor check 14 gt 10 M C SC term task element A term signal_ended matched value uq us enum unbetoncedl A term data_format matched value Mi us enum analog A term Connection establish matched datda Pua aS eneh hot _pluggableJ accept submatch match factor check 4 gt M C SC term electrical C SC term characteristics A term classification matched value ug us enum externa A term Classification matched value ug us enum external HEHHEHE HHHH HHHH FEET EEE ET EEE ETE ETE TEETH ETE EEE TEEPE ttt et checking have an acceptable RQGroup match comparing match factors is 26 gt 42 gt gt gt gt gt gt gt try another DGroup dgroup3 from Device red_1 imic2_1 HEHHEHE HHHH HHHH HHHH EE ET EEE EEE ETE TEETH ETE TEETH HHHH lt gt checking availability of Registration Unit audio_stream_in available A term direction matched value uq us enum analog_to_digital A term sampling rate m
80. with IO Discovery passing notification to IO_Results to cancel all match results involving the system The computer system indicated by the shaded area is the one where a system disconnect is raised and the boxed area represents services on remote systems The task begins by referencing stored results to reverse those involving that system For each match with a device IO_Resources is advised to remove record of resource allocation If the device acted as a requester or for requesters themselves then IO Outlets tears down record of the match Notification is also passed to other systems that need to cancel matches but did not receive the event directly They utilise their IO_Results service to perform match reversals Where device resources have become available matching is triggered and composition notified on the appointed system local remote cancel_all_matches involving_system 2 2 ier cancel_match_from device ___ p anes See te er match i cancel_match_from requester I T T permatch erform_match Poor E od I T remote remote remote local cancel all_matches jens system aoe multicast cancel match_from i oe ee I lien permatch cancel_match_from pr aad i p perimatch ais Benes ere a l perform_ match i peo el figure 3 9 system disconnect notes solid lines indicate sequences which occur whereas broken lines ma
81. 00 status threshold 180 DEVICES 2 525 2S a aa a ee eee d1 gt Device red_1 imic2_1 Node red connected Spec imic2 RegistrationUnits audio_stream_in available audio_stream_out available d2 gt Device green_2 us224_1 Node green connected Spec us224 RegistrationUnits analog_audio_stream_out unavailable analog_audio_stream_in available d3 gt Device blue_3 audiophile_1 Node blue connected Spec audiophile RegistrationUnits analog_audio_stream_in unavailable analog_audio_stream_out unavailable 181 182 e o Bibliography Abowd G D Bobick A F Essa I A Mynatt E D amp Rogers W A 2002 The Aware Home A living laboratory for technologies for successful aging American Association for Artificial Intelligence AAAT Technical Report WS 02 02 GVU Center Georgia Institute of Technology Atlanta GA USA Advanced Micro Devices Inc 2009 AMD I O Virtualization Technology IOMMU Specification rev 1 26 34434 AMD Allegro Software Development Corporation 2006 Networked Digital Media Standards A UPnP DLNA Overview white paper Allegro ALSA Project 2007 Advanced Linux Sound Architecture ALSA ver 1 0 14rc3 device driver for Linux OS ALSA Project Anderson D 2001 USB System Architecture USB 2 0 2nd ed Addison Wesley Reading MA USA ISBN 0 201 46137 4 Apple Inc 2000 Fundamentals of Open Firmware technote TN1061 1062 1044 Apple Cupertino CA
82. 16 data audio_in_settings Request rq4 Request Group rqgroup3 data_channels system integer 2 data audio_in_settings Request rq4 Request Group rqgroup3 sampling_rate frequency hertz 48000 retracting existing match transaction cancelling existing match for Request rq5 involving Request Group List rqgroup4 cancelling existing match for Request Group rqgroup4 involving Device Group dgroup2 from Device red_1 imic2_1 match factor 26 apply match with Device red_1 imic2_1 MODE remove Request Group rqgroup4 Device Group dgroup2 registration units audio_stream_out updated gt available state update term bit_resolution maps gt state dac_resolution value system bit 16 with no retained state found state update term data_channels maps gt state dac_channels value system integer 2 with no retained state found state update term sampling_rate maps gt state dac_sample_rate value frequency hertz 48000 with no retained state found apply match with Requester black_5 requester_1 MODE remove code adjust_dac_settings Request rq5 Request Group rqgroup4 gt DeviceCodeInterface dac_configure set_sample_rate set_resolution set_channels data audio_out_settings Request rq5 Request Group rqgroup4 bit_resolution system bit 16 data audio_out_settings Request rq5 Request Group rqgroup4 data_channels system integer 2 data audio_out_sett
83. 2 Later when applying the results with the requester the annotation is used to link to a table containing external data parameters Although initially empty it becomes populated as match results are applied Implementation specifics The implementation links to data parameters in requesters through annotations at the leaf level for example appearing with sampling rate data_channels amp bit_resolution aspects 1st square bracket in a structural description task_element 1 l adjust_dac_settings 0 14 task O 11 function 0 91 direction 5 ug us enum digital_to_analog sampling_rate audio_out_settings 2 frequency hertz 48000 data_channels audio_out_settings 1 system integer 2 bit_resolution audio_out_settings 1 system bit 16 When applying the results with the requester the annotations in the results link to a table fact for managing access to external data parameters outletDataInterfaceList requester audio_out_settings Once the table is populated with matched parameters they appear as further facts dataInterfaceTable requester outlet1 composite_rq1 rql rqgroup1 audio_out_settings bit_resolution system bit 16 dataInterfaceTable requester outlet1 composite_rq1 rql rqgroup1 audio_out_settings data_channels system integer 2 dataInterfaceTable requester outlet1
84. 4 3 Managing Backtracking 6 Conclusion 6 1 Accomplishments 6 1 1 System Services 6 1 2 Taxonomy and Structural Description of Devices 6 1 3 Definition of the Process of Composition 6 2 Impact of Our Contribution 6 2 1 Achieving Context Awareness 6 2 2 Driverless Operating System 6 2 3 Matching Linked to Connection Events 6 2 4 Type System Evolution 6 2 5 Describe Devices to be Granted Access Appendices Appendix A Audio Device Description A 1 1 Griffin iMic v2 A 1 2 M Audio Audiophile USB A 1 3 Tascam US 224 A 1 4 Device Comparison Appendix B A Worked Example B 1 1 Introduction B 1 2 The Participants B 1 3 The Distributed System B 1 4 The Match Process Bibliography xi 124 125 127 130 130 132 133 136 139 139 139 140 143 143 143 144 144 145 145 145 146 146 146 147 147 147 150 153 156 158 158 158 160 162 183 xii List of Figures 2 1 device and driver code dependencies upon system elements 2 10 Universal Serial Bus USB Class Codes 2 14 doing with images makes symbols model 3 2 typical physical organisation of a system 3 3 sphere of device responsibility example 3 4 physical system connection topology example 3 5 computer system organisation incorporating a processing module 3 6 device connect 3 7 device disconnect 3 8 system connect 3 9 system disconnect 3 10 requester create 3 11 requester cancel 3 12 perform match preamble 3 13 perf
85. 8000 amp retained value frequency kilohertz 44 1 completed applying RQGroup match to Device to constrain resource availability gt completed matching entire RQGroup list for Request rq4 X checking have derived a match for Request rq4 adding match for Request rq4 to match list for Request Alternative composite_rq3 next Request rq5 with RQGroup list rqgroup4 gt gt gt gt gt try another Device green_2 us224_1 next RQGroup rqgroup4 gt gt gt gt gt gt gt try another DGroup dgroup21 from Device green_2 us224_1 FHEHELEHELEP ETE PETE Ett ttt ttt ttt ttt ttttettttttttttttt ttt HEHHEHE ETE EE HHHH HHHH FEET PETE TEETH EEE EEE TEEPE TEE EE checking have an acceptable RQGroup match comparing match factors is gt 23 gt gt gt gt gt gt gt try another DGroup dgroup22 from Device green_2 us224_1 FHEHHLEHELE HTH HHT ttt ttt ttt ttt ttt ttt ttt ttt pr eshecking availability of Registration Unit anatog_audio_strean_in A term operate matched value uq us enum required C tern approach C term control A term direction matched value ugus enum unidirectional 1 A term logical_channels matched value system integer 2 A term signal_format matched value ug us enum digital A term model matched value ug us enum stream accept submatch match factor check M C SC t term conpression matched value A term data_format matched value accept submatch match facto
86. Clength mm 8 37 C SC term physical dimensions C SC term physical_manifestation A term connector matched value uq us enum rca_connector rca_connector A term classification matched value ug us enum externat 1 A term device boundary matched value sYst n bootean true term relat C term Togteat structure A term connector matched value _fug us enum rca_connector rca_connector A term classification matched value uq us enum external A term device boundary matched value syst m boolean true C term relation C term logical_structure A term signal ended matched value ug us enum unbalanced A term data_format matched value ug us enum tanal A term conn ction establish matched value Ta ae ened Chot_pluggable accept submatch match factor check 4 gt M C SC term electrical M C SC term characteristics A term classification matched value uq us enum externa A term classification matched value uq us enum external FHEPELEET ETE EE EEE ET FEET EEE ET EEE EEE ETE EE ETE ETE TEETH TEETH checking have an acceptable RQGroup match comparing match factors is 26 gt 42 ERROR no match found for RQGroup rqgroup1 with Device green_2 us224_1 reversing application of group matches so far with same device aborting Request List at rq2 amp returning null match X checking have derived a match for Request rq2 ERROR no match found for Request rq2 reversing applicati
87. D amp Pratt I 1994 Devices on the Desk Area Network IEEE Journal on Selected Areas in Communication vol 13 4 DOI 10 1109 49 382162 pp 722 732 Bavier A Voigt T Wawrzoniak M Peterson L amp Gunningberg P 2002 SILK Scout Paths in the Linux Kernel technical report 2002 009 Uppsala University Sweden Department of Information Technology Bershad B Savage S Pardyak P Sirer E G Fiuczynski M E Becker D Chambers C amp Eggers S J 1995 Extensibility Safety and Performance in the SPIN Operating System In Proceedings of the 15th ACM Symposium on Operating System Principles SOSP DOI 10 1145 224056 224077 pp 267 284 Bluetooth SIG Inc 2009 Bluetooth Core Specification version 4 0 Bluetooth SIG Brown A B amp Seltzer M I 1997 Operating System Benchmarking in the Wake of Lmbench A Case Study of the Performance of NetBSD on the Intel x86 Architecture In Proceedings of the ACM SIGMETRICS International Conference on Measurement and Modelling of Computer Systems DOI 10 1145 258612 258690 pp 214 224 Buxton W A S 1983 Lexical and Pragmatic Considerations of Input Structures Computer Graphics vol 17 1 DOI 10 1145 988584 988586 pp 31 37 Card S K MacKinlay J D amp Robertson G G 1990 The Design Space of Input Devices Proceedings of the SIGCHI Conference on Human Factors in Computing Systems CHI 90 DOI 10 1145 97243 97263 pp 117 124 Card S K
88. DIF digital audio stream to PCM digital audio stream e evaluate an input by performing a function with the result as output requires specifying the function e g extract encapsulated control command from USB packet e translate user interface signals to from digital requires listing the mapping to from user interface from to CL e g digital encode of slider input from audio control surface e director to marshall outputs or serialise inputs specify criteria for an input to be marshaled to particular outputs or Sserialisation policy for set of inputs to an output e g USB interconnect interface on device sending or receiving data packets A need may arise where fine adjustments are necessary or an additional role is required In any case the impact to the taxonomy would be limited to low level details within the role category for a task element The role breakdown serves as an exploratory vehicle for describing the devices investigated Future work could partake of the opportunity to model 101 driver behaviour or control aspects of a device In which case techniques such as Petrie Nets and Executable UML state transition descriptions would be useful Schattkowsky and Muller 2004 Mendes Leitao et al 2008 Zakaria Kimura et al 2009 Sectioning a device description At this stage we are managing to generate a description that provides coverage of a whole device in terms of modules However empirical work revealed a problem with using
89. Digital Living Network Alliance 2013 When a new device is added it advertises to the network Whereas when adding new control points they seek to discover devices Any interested control point can listen for device available notifications Whereas all devices 36 must listen for search requests The process is conducted by listening then matching and responding if successful Microsoft s HomeOS presents an abstraction where all devices appear to be connected to a single logical PC Dixon Mahajan et al 2012 Composition happens in the form of determining whether an application will be able to function with the device services currently available in the home This occurs when adding a new application The management system software compares role names and compiles a list of device services corresponding to the application request The iRoom interactive spaces implementation provides infrastructure support for user interface selection adaptation generation Ponnekanti Lee et al 2001 Composition happens in the context of needing to generate a user interface for control of services implemented by devices or applications User appliances e g access input devices request user interfaces for services from the management infrastructure interface manager When a request is received the interface manager selects a generator based on the requesting appliance and the service for which the user interface was requested Once generated the u
90. E EET EE ETE EET EET EET EEE TEE TEETH Ett tt ttt gt checking availability of Registration Unit audio_stream_out available A term sampling_rate matched value frequency hertz 48000 A term data_channels matched value system integer 2 A term bit_resolution matched value system bit 16 A term principal matched value ug us enum convert SC term role SC term task A term operate matched value uq us enum required f term approach s S C term control A term operate matched value uq us enum required C term approach C SC term control A term direction matched value uq us enum unidirectional A term logical channels matched value system integer A term signal_format matched value ug us enum digital A term model matched value uq us enum stream accept submatch match factor check 6 gt 4 M C SC term Link A term compression matched value uq us enum uncompressed A term data_format matched value uq us enum pcm_audio accept submatch match factor check 6 gt 5 M C SC term channel M C SC term primitives accept submatch match factor check 12 gt 9 M C SC term conminications Link gt checking availability of Registration Unit audio_stream_out available A term configure matched value uq us enum required SC term approach SC term control A term principal matched value uq us enum adjust SC term role C
91. FEET EEE ET EEE ET EET EEE HHHH HHHH checking have an acceptable RQGroup match comparing match factors is gt 23 gt gt gt gt gt gt gt try another DGroup dgroup22 from Device green_2 us224_1 HEHEHHE HHHH HHHH HHHH HHHH EE EET PETE EE ETE ETE EEE TEEPE TEETH gt checking availability of Registration Unit analog_audio_stream_in available A term direction matched value uq us enum analog_to_digital A term sampling_rate matched value frequency hertz 48000 A term data_channels matched value system integer 2 A term bit_resolution matched value system bit 16 accept submatch match factor check 9 gt 9 M C SC term function A term principal matched value uq us enum convert M C SC term role M C SC term task accept submatch match factor check 14 gt 14 M C SC term task_element A term direction matched value uq us enum unidirectional A term logical_channels matched value system integer 2 A term signal_format matched value uq us enum digital A term model matched value uq us enum stream accept submatch match factor check 6 gt 4 M C SC term Link A term compression matched value uq us enum uncompressed A term data_format matched value uq us enum pcm_audio accept submatch match factor check 6 gt 5 M C SC term channel M C SC term primitives accept submatch match factor check 12 gt 9 M C SC term communications_Link FHEFETEET HHH
92. H EEE ETE ETE EE ETE EEE TEETH EEE t Ett checking have an acceptable RQGroup match comparing match factors is 28 gt 23 RQGroup match found with DGroup dgroup23 from Device green_2 us224_1 adding match for RQGroup rqgroup1 to match list for Request rq1 apply match with Device green_2 us224_1 MODE apply Request Group rqgroup1 Device Group dgroup23 registration units analog_audio_stream_out updated gt unavailable state update term bit_resolution maps gt state dac_resolution new value system bit 16 amp retained value system bit 16 state update term data_channels maps gt state dac_channels new value system integer 2 amp retained value system integer 2 state update term sampling_rate maps gt state dac_sample_rate new value frequency hertz 44100 amp retained value frequency kilohertz 44 1 completed applying RQGroup match to Device to constrain resource availability gt completed matching entire RQGroup list for Request rq1 X checking have derived a match for Request rq1 adding match for Request rqi to match list for Request Alternative composite_rq1 gt completed matching entire Request List for Request Alternative composite_rq1l X checking have derived a match for Request Alternative composite_rql MATCH RESULT match found match for an inactive Outlet there is no pre existing match to cancel completing apply of new match removing shadowed st
93. H HHHH HHHH H HHHH EE EET EET EEE ETE ETE TEETH EE ETE ETH checking have an acceptable RQGroup match comparing match factors is 26 gt 23 RQGroup match found with DGroup dgroup22 from Device green_2 us224_1 adding match for RQGroup rqgroup3 to match list for Request rq4 apply match with Device green_2 us224_1 MODE apply Request Group rqgroup3 Device Group dgroup22 registration units analog_audio_stream_in updated gt unavailable state update term bit_resolution maps gt state adc_resolution new value system bit 16 amp retained value system bit 16 state update term data_channels maps gt state adc_channels new value system integer 2 amp retained value system integer 2 state update term sampling_rate maps gt state adc_sample_rate new value frequency hertz 48000 amp retained value frequency kilohertz 44 1 completed applying RQGroup match to Device to constrain resource availability gt completed matching entire RQGroup list for Request rq4 X checking have derived a match for Request rq4 adding match for Request rq4 to match list for Request Alternative composite_rq4 gt completed matching entire Request List for Request Alternative composite_rq4 168 X checking have derived a match for Request Alternative composite_rq4 MATCH RESULT match found match for an inactive Outlet there is no pre existing match to cancel completing apply of new mat
94. Intelligent Discovery Configuration and Composition of Devices ina Distributed System Nicole Katyan Thesis submitted for the degree of Doctor of Philosophy in the School of Computer Science Faculty of Engineering Computer and Mathematical Sciences The University of Adelaide Adelaide SA 5005 AUSTRALIA 2014 ii Abstract Establishing access to the functionality of input output devices across a distributed system presents significant challenges worth investigating To accomplish this requires locating devices and understanding their identity so that requests for them can be satisfied Current systems require the domain of requestable devices be resolved beforehand and that they be identified as discrete items Additionally configuring devices only happens if an operating system has access to suitable drivers and composition is conducted by middleware applications without any system service awareness These approaches restrict device use in a distributed context and fail to provide a satisfactory solution This research has the goal of accomplishing access to devices in a distributed system without such constraints We present an approach where devices are described by a language based upon a rich taxonomy of form and function Requests for devices are formulated using the same language and a matching process is employed to satisfy requests The devices capable of being matched may be rich in functionality complex consist of sub unit
95. Johanson Fox et al 2002 A management framework discovers information in the following ways vi services periodically broadcast their presence to a managing service which includes service descriptions e g operations supported amp their parameters written in a service description language vii when an appliance requests a user interface from the managing service it supplies an appliance description that provides information about the appliance e g pixels viii information about the workspace context is contained in a central datastore this includes physical locations and dimensions of various devices e g lights amp displays descriptive information about devices e g display1 is the front display and device relationship information e g projector2 projects onto display screen1 Multicasting Bonjour an Apple implementation of Zeroconf is a service discovery protocol for locating devices and the services that their operating systems offer on a local network Apple 2005 Cheshire and Steinberg 2005 It is intended to work within a single broadcast domain typically a small IP based network using Ethernet IEEE802 interconnect without Domain Name System DNS configuration The core component for service discovery is Multicast DNS mDNS implemented across a local network by computer systems storing their own list of DNS resource records When a mDNS client wants to know an address given a n
96. Ling rate matched value frequency hertz _ 48000 A term data_channels matched value system integer i A term bit resolution matched value system bits 16 A term principal matched value uq us enum convert C term role C term task A term operate matched value uq us enum required C term approach C term control A term operate matched value uq us enum required C term approach C term control A term direction matched value uq us enum unidirectional A term Logical channels matched value system integer 21 A term signal_format matched value uq us enum digital model matched value ug us enum strean accent Ssubnatch match factor checi M C SC t A term compression matched value ug us enum uncompressed term data format matched value yq us enum pem_audio accept cusmue cis pateh factor check s M C SC term channel M C SC term primitives accept submatch match factor check 12 gt 9 M C SC term conminications tink gt checking availability of Registration Unit qudio_stream_out available A term configure matched value uq us enum required M C SC term approach M C SC term control cel term principal matched value uq us enum Codjust MACS C term task A term configure matched value uq us enum required A term operate matched value uq us enum required M C SC term approach M C SC term control A term configure matched
97. List X attemptMatchUsingRQList _ _ CompRQ _ RQH _ MatchList where unable to satisfy any request return a null match for alternative remove matches applied to Device s that were bound to requests tried earlier removeDMat chApply0fRequests MatchList L CUT removeDMatchApply0fRequests removeDMatchApply0fRequests RQMH RQMT removeDMat chApplyOfGroups RQMH removeDMatchApply0fRequests RQMT Notes removeDMatchApplyOfGroups goal is described under the next heading 5 3 3 Satisfying a Request Guidance on satisfying a request concerns RQGroups contained in a list associated with them It makes certain that satisfaction means every RQGroup is sufficiently matched How did it come about Without lists of RQGroups or even the concept of a RQGroup or DGroup it is possible for the search to match modules in an uncertain manner from anywhere in a device description It could be a single module matches from disparate elements of a device and yet a requester may require that multiple modules match to ensure an adequate description We allow a request to specify module associations in a structural description referring to such as a RQGroup and seek the same within a device This allows a requester control over expression of association This is about improving the quality of satisfaction by guiding the process as to how a particular request is to be matched when presented with complex and varied functionality i
98. Q I Dearle A Morrison R amp Rosenberg J 1990 Type Equivalence Checking in Persistent Object Systems In A Dearle G M Shaw amp S B Zdonik eds Implementing Persistent Systems Morgan Kaufmann pp 151 164 Control4 2013 Control4 Home Automation System System User Guide 200 00001 rev S OS 2 5 2 Coulouris G Dollimore J Kindberg T amp Blair G 2012 Distributed Systems Concepts and Design 5th ed Addison Wesley ISBN 0132143011 Digital Equipment Corporation 1984 R7 11 Software Support Manual v 5 1 DEC Digital Living Network Alliance 2013 DLNA Network Device Interoperability Guidelines Overview viewed December 2013 lt http www dIna org dIna for industry technical overview gt Distributed Management Task Force 2013 System Management BIOS SMBIOS Reference Specification v2 8 0 specification DSP0134 DMTF Dixon C Mahajan R Agarwal S Brush A J Lee B Saroiu S amp Bahl P 2012 An Operating System for the Home In Proceedings of the 9th USENIX conference on Networked Systems Design and Implementation NSDI Dong H Hussain F K amp Chang E 2013 Semantic Web Service matchmakers state of the art and challenges Concurrency amp Computation Practice amp Experience vol 25 7 pp 961 988 Edge Magazine Inc 1995 Parallel technology enters VRcades Edge no E9 June Future PLC ISSN 1350 1593 185 Edwards W K Newman M W
99. R DV MatchQ MatchS MatchR Matchv unitConversion RQQ RQS RQV BaseRQS BaseRQV unitConversion DQ DS DV BaseDS BaseDV if RQ amp D are the same unit quantity then bind match else fail RQQ DQ MatchQ RQQ both RQ amp D must be same base unit symbol BaseRQS BaseDS rangeValue RQR BaseRQV DR BaseDV MatchAR BaseMatchV no conversion of base match symbol to RQ MatchS RQS unitConversion MatchQ BaseRQS BaseMatchV MatchS MatchV unitConversion _ _ _ V NewV reverse V NewV unitConversion Q S VH VT NewS V Y conversion Q S VH NewS NewV unitConversion Q S VT NewS NewV V Y sample of facts used to perform unit conversions amp determine range overlap conversion length m AV cm NewAV NewAV is 100 x AV rangeValue gt RQV DevAV DevAV RQV lt DevAV 5 2 5 Managing State Motivation Including data of relevance to conducting composition is the intention behind providing logical visibility to state They may already be data variables however it is linking them with composition that matters We also set out to ensure adjustments to state are automatic as a result of applying or removing a match with the participants 125 Illustrative example Our motivation towards the visibility of state is the spread of data parameters associated with a device and its driver code Using the example of an audio codec device the Griffin
100. Requirements of a System 2 5 1 Trends and Contexts 2 5 2 Arriving at the Technical Requirements 3 The Distributed System 3 1 Distributed Services 3 1 1 Distributed Agreement 3 1 2 Service Architecture for Composition 3 2 IO_Discovery Service 3 2 1 Tasks Performed by the IO_Discovery Service 3 2 2 Implementing the IO Discovery Service 3 2 3 Interconnect Specification Changes 3 2 4 Requirements of Device Descriptions 3 2 5 Protocol Definitions 3 2 6 Records Maintained 3 2 7 Changes to Computer System Specifications 3 3 IO Configuration Service 3 3 1 Tasks Performed by the IO_Configuration Service 3 3 2 Implementing the IO Configuration Service 3 3 3 Interconnect Specification Changes 3 3 4 Requirements of Device Descriptions 3 3 5 Protocol Definitions 3 3 6 Records Maintained 3 3 7 Changes to Computer System Specifications 3 4 IO Composition Service 3 4 1 Tasks Performed by the IO Composition Service 3 4 2 Implementing the IO_Composition Service iii Vii xiii 3 4 3 Requirements of the Match Process 3 4 4 Requirements of Device Descriptions 3 4 5 Protocol Definitions 3 4 6 Changes to Computer System Specifications 3 5 Support Services 3 5 1 IO Resources 3 5 2 IO Requesters 3 5 3 IO Outlets 3 5 4 IO Results 3 6 Event Sequencing 3 6 1 Device Connect 3 6 2 Device Disconnect 3 6 3 System Connect 3 6 4 System Disconnect 3 6 5 Requester Create 3 6 6 Requester Cancel 3 6 7 Perform Match Taxonomy and Structural Descr
101. SC term Lini K term conpression matched value ug S enum Funconpressed A term data_format matched value uq us enum pcm_audio cept submatch match factor check 6 gt 5 SC term chanhel a C CESC term primitives accept submatch match factor check 12 gt 9 I C SC term communications_link A term principal matched value uq us enum adjust C SC term role C SC term task p echacking availability of Registration Unit analog oudio_strean_in available A term configure matched value uq us enum required SE term approach SC term control A term principal matched value uq us enum adjust SC term role SC term task A term data format matched value fug us enun digital A term signal_mute matched value system boolean true M C SC term function A term principal matched value uq us enum adjust M C SC term role M C SC term task A term configure matched value uq us enum required A term operate matched value uq us eum Pequired M C SC term approach M C SC term control accept submatch match factor check 14 gt 10 M C SC term task element A term data_format matched value uq us enum analog A term connection establish matched value ogee onda Chot_pluggable accept submatch match factor check 3 gt M C SC term electrical M C SC term characteristics A term direction matched value _fug us enum input A term classification matched
102. SC term task A term configure matched value uq us enum required A term operate matched value uq us eum Pequired C term approach C term control A term configure matched value ug us enum Crequined A term operate matched value uq us eum Pequired C term approach C term control A term data_format matched value uq us enum digital A term signal_mute matched value system boolean true M C SC term function term principal matched value ug us enum adjust role M C SC term task A term configure matched value uq us enum required A term operate matched value uq us enum required C term approach C term control ept submatch match factor check 14 gt 10 A term signal_ended matched value uq us enum unbalanced A term data_format matched value fug tis enum analog A term conn ction_establish matched valu ud us enum hot_pLuggable accept submatch match factor check 4 gt 2 C SC term electrical CSC term characteristics A term classification matched value fuq us enum external 1 A term classification matched value uq us enum external HEHHEHE HHHH HHHH EEE ET EEE ET EEE EEE ETE EE ETE ETE TEE TEEPE TEEPE checking have an acceptable RQGroup match comparing match factors is 26 gt 42 gt gt gt gt gt gt gt try another DGroup dgroup3 from Device red_1 imic2_1 HEHHEHE HHHH HHHH EEE ETE TEESE EEE ETE ET EE EET PETE TEETH EEE TEE
103. SUS Ehun Leet A term direction matched value uq us enum input A term classification matched value ug us enum external A term signal_ended matched value ug us enum unbalanced A term data format matched value uiq us enum tanalog connection establish matched value ug us enum Lhot_pluggable chook Submaeeh match Factor Check a M C SC term electrical M C SC term characteristics A term direction matched value uq us enum input A term classification matched value ug_us enum externat J A term direction matched value uq us enum input A term classification matched value ug us enum Texssona1 A term data_format matched value ug us enum Lan A term connection establish matched value Lua as ened Chot_pluggable accept submatch match factor check 3 gt M C SC term electrical M C SC term characteristics A term direction matched value A term classification matched val A term direction matched value A term classification matched val A term signal ended matched value uq us enum unbalanced A term data_format matched value Mi us enum analog A term Connection establish matched dalda LUA Us etm hot pluggableJ accept submatch match factor check 4 gt SC term electrical SC term characteristics A term direction matched value ug us enum input A term classification matched value uq us enum external A term direction matched value
104. TH EEE TEETH TEETH ttt checking have an acceptable RQGroup match comparing match factors is 40 gt 42 jus enum input a us renum Beeraatn gt gt gt gt gt gt gt try another DGroup dgroup23 from Device green_2 us224_1 FHEHHLETELE PETE PEt ttt ttt ttt tt ttt ttt ttttttttttttttt ttt gt checking availability of Registration Unit analog_audio_stream_out A term operate matched value uq us enum required C term approach C term control A term direction matched value ug us enum unidirectional A term logical_channels matched value system integer A term si mal_format matched value uq us enum digital erm model matched value ug us enum strean accept Submatch notes taxes chec M C SC term link K term compression matched value uq us enum unconpressed A term data_format matched value yq us enum pem_audio accept submatch match factor check 6 gt M C SC term channel M C SC term primitives accept submatch match factor check 12 gt 9 MC communications link A term principal matched value uq us enum Ladjust M C SC term role M C SC term task A term principal matched value uq us enum adjust M C SC term role M C SC term task A term principal matched value uq us enum adjust M C SC term role M C SC term p echacking availability of Registration Unit analog audio_strean_out A term configure matched value u
105. Temperature Pressure Touch Softness Texture Roughness Sharpness Scent Smell Odor Aroma Sour Salt Taste Sweet Bitter Radial Symmetry 2D Asymmetry ne Bilateral Symmetry Regularity Asymmetry Egocentric Orientation Immediate Exocentric Distant figure 4 5 input output model of the human senses Properties related to the interface and interaction A series of groupings emerge as properties are distilled from the material we presented Of importance is identifying the user interface as a distinct element and to indicate it physically manifests in the environment This extends to the functionality provided by the device as being implemented by physical elements Even to noting whether the interface presented is self contained or contributes to a larger grouping Further aspects are to describe an interface by outlining the sensory dimensions applicable to interaction with the device Then to look at detailing the mechanical structure of the interface and for each element to show the primitive sets of steps covering how they operate Expressed as a series of terms that characterise these properties they break down as i user interface functionality e g physical interface e g physical discreteness e g self ii sensory mapping primary e g touch secondary e g sensation aspect e g pressure iii mechanical structure interface element e g switch element subtype e g slider switch direction e g input
106. USA Apple Inc 2005 Bonjour Printing Specification v1 0 2 Apple Apple Inc 2007 Introduction to I O Kit Fundamentals Apple Apple Inc 2009 I O Kit Device Driver Design Guidelines Apple Apple Inc 2009 Universal Binary Programming Guide 2nd ed Apple Arnold K 1999 The Jini Architecture Dynamic Services in a Flexible Network In 36th ACM IEEE CAS EDAC Design Automation Conference DAC pp 157 162 Asahi Kasei Microsystems Co Ltd 2004 AK4528 High Performance 24Bit 96kHz Audio CODEC datasheet MS0011 E 01 Aukstakalnis S amp Blatner D 1992 Silicon Mirage The Art and Science of Virtual Reality Peachpit Press Berkeley CA USA ISBN 0 938151 82 7 Baecker R M amp Buxton W A S eds 1987 Readings in Human Computer Interaction A Multidisciplinary Approach Morgan Kaufmann San Mateo CA USA ISBN 0 934613 24 9 Banga G Druschel P amp Mogul J C 1999 Resource Containers A New Facility for Resource Management in Server Systems Proceedings of the 3rd Symposium on 183 Operating Systems Design and Implementation OSDI New Orleans LA USA pp 45 58 Barham P Dragovic B Fraser K Hand S Harris T Ho A Neugebauer R Pratt I amp Warfield A 2003 Xen and the Art of Virtualization Proceedings of the 19th ACM Symposium on Operating System Principles SOSP Bolton Landing NY USA DOI 10 1145 945445 945462 pp 164 177 Barham P Hayter M McAuley
107. USB Forum USB Implementors Forum 2011 USB Class Codes viewed March 2014 lt http www usb org developers defined_class gt Varga A 2010 Unibus Systems and Options viewed March 2014 lt http hampage hu dr unibus html gt Via Technologies Inc 2001 VT6306 PCI Firewire 1394a Integrated Host Controller Firewire 1394a OHCI Link Layer Controller with Integrated 400Mbps 3 Port PHY for the PCI Bus datasheet rev 1 11 Via Taipai Taiwan Waldo J 1998 Jini Architecture Overview technical white paper Sun Microsystems Inc Palo Alto CA USA Want R Pering T Sud S amp Rosario B 2008 Dynamic Composable Computing In Proceedings of the 9th Workshop on Mobile Computing Systems and Applications HotMobile 08 DOI 10 1145 1411759 1411765 pp 17 21 Weerawarana S Chinnici R Gudgin M amp Canon J J M 2002 Web Services Description Language WSDL v1 2 W3C viewed February 2014 lt http www w3 org TR wsdll2 gt 193 Western Digital Technologies Inc 2010 WD Caviar Blue Desktop Hard Drives specifications overview viewed March 2014 lt http www wdc com en products products aspx id 770 gt Western Digital Technologies Inc 2010 WD SiliconEdge Blue Solid State Drives specifications overview viewed March 2014 lt http www wdc com wdproducts library SpecSheet ENG 2879 771357 pdf gt Whitaker A Shaw M amp Gribble S 2002 Denali Lightweight V
108. a minimal specification of system services defines those relevant to creating a distributed system and handling device configuration and composition The other option is to define an explicit software layer for distributed communication between existing systems using current infrastructure These systems may employ a variety of operating systems They form a distributed system by running middleware that defines protocols for communication between them across existing networks A distributed operating system is not well suited to our needs because it mandates considerable software outside of device handling In constraining each computer system to a broader system software implementation this makes it harder to articulate the changes needed or stipulate the requirements for implementing our approach to dealing with 43 devices It also provides an abstraction of there being a single system which defeats the purpose of our focus on the problem of remote access to resources Middleware is not advisable because it assumes a computer system has already been configured by an operating system Whereas our concern is for the low level interaction between hardware and software There are configuration issues on a computer system that need to be addressed and as well as making it possible to discover device connections We are seeking to reduce the changes required for a distributed system yet tackle the challenges facing them in a comprehensive fashion Th
109. a_format mechanical_structure structures connector classification direction 1 us enum analog_to_digital frequency hertz 48000 system integer 2 u 1 1 system bit 16 La q r 1 01 ug us enum convert 1 1 uq us enum uncompressed uq us enum pcm_audio uq us enum digital system boolean true uq us enum adjust uq us enum unbalanced ug us enum analog q us enum rca_connector rca_connector q us enum input uq us enum external c cC m requestGroup requester rqgroup2 taskflow _ task_element 1 lelectrical_interface 1 1 communications_link 1 1 01 1 106 4 5 2 Adding Dimensions to Requests The base definition of a request underwent considerable experimentation which revealed a need to expand their expression The motivation was to make a description of a sought after device more flexible and to allow compromises by providing options where an ideal device is not available These dimensions are accomplished by multiple requests being brought together and expressed as combinations Then to permit separate request combinations The intention is to compose a combination and if needed a further combination is tried when failure occurs Each of t
110. ability mating force during card insertion operating temperature thermal shock B Electrical level signal definition contact pin assignment connector expansion card 1 synchronous timing signaling clock amp bus timing specifications ii physical requirements contact amp insulation resistance capacitance current voltage rating signal loading power dissipation iv power provision system mainboard v engineering implementation clock skew reset assertion control signals mainboard trace length limits expansion card C Bus Operation level i commands types usage rules i i v timing latency considerations vi other bus operations device selection interrupt acknowledge vil error functions parity generate check error reporting recovery figure 4 6 PCI elaboration of engineering specifics 82 These distinctions are interconnect specific but they demonstrate a depth to device description despite lacking logical visibility Mechanically the specification stipulates requirements for a system platform connector and for devices as adapter cards The electrical level assigns signal lines to contacts at the connection point with attention paid to timing constraints outlined for signaling with reference to a clock The purpose of pins at this interface are defined then an indication of expected timing for correspondence between groups of signaling lines The effect is to overlay the phy
111. ablish or remove record of device resources As part of composition it performs checks of records to determine whether any device has resources available with the process triggered as an affirmative response During the match process this service responds to a cluster wide call by submitting devices with resources available An initial resource record is established when devices are configured for operation and adjusted as results are applied or removed This service provides a way of checking an entire system for device resource availability 3 5 2 IO_Requesters The JO_Requesters support service is concerned with managing requesters and is called upon to allocate system memory and ready them for execution These actions are performed as a requester is deployed to execute on a computer system The extraction point could be from another system or a persistent storage unit for software This service draws upon an understanding of the specification for a requester to perform transfer and setup We define the structure of a requester in the next chapter Once a requester is ready IO_Requesters notifies all systems within a cluster to check for device resource availability possibly leading to a triggering of composition When a requester leaves an orderly tear down of structures happens The freeing of device resources by virtue of cancelled requests leads to a triggering of the match process 3 5 3 IO Outlets The primary role of the JO Outle
112. access It also specifies the mechanisms through which logical access is to be performed and organises the manner in which the device is to respond when this happens These aspects are outlined with reference to the Firewire interconnect 15 At a basic level an interconnect determines how a device attaches to a computer system It determines the physical characteristics of that connection from the manifestation of the actual connector through to the particulars of electrical signaling By designing a device for attachment across an interconnect it is implied that the underlying specification has been adhered to in its entirety The Firewire specification details a range of connectors that can be employed From the physical dimensions through to the mechanical properties it is expected that any use of them in a device is fully compliant Provisioning of device power across the interconnect is possible by virtue of cabling options permitted as a result of the connector employed as is shown in figure 2 3 7 1mm 6 3mm 6 4 2 pins 1 1 power supply 5 4mm 2 ground 3 4 signal line A 5 3 1 5 6 signal line B _ 11mm Firewire 400 6 pin connector Firewire 400 4 pin connector figure 2 3 Firewire 400 4 or 6 pin cable connector IEEE 1995b 93 IEEE 2000 79 At a different level the specif
113. ach to the issue of brittleness to device configuration accounts for the trend of heightened frequency to encounters with new devices 5 adopt an abstraction that provides a rich description of devices and is based on actual hardware this attends to the restrictions inherent in using named types for devices and provides a means of describing devices not yet developed it considers greater expressiveness required for multimedia services and formulating requests for devices embedded in the environment 6 define a process of composition that dynamically determines who participates when and where it is conducted in a distributed system provides a more flexible process for satisfying requests targets the trend of mobility with variable connectivity requiring a more robust approach to matching 7 link the stages together tying establishing access to the process of composition then linking configuration and composition to discovery addresses the need for greater reliability acknowledges the overall influence the trends have upon distributed systems 42 3 The Distributed System In this chapter we take the requirements for distributed services and present a design for them At each stage from discovery through configuration to composition the requirements and changes necessary to implement the distributed system are outlined 3 1 Distributed Services Our aim is to create a highly responsive distributed system that will have the cap
114. acity to endure From the outset we would like to minimise the extent of distributed agreement required for its construction Hence the system being built does not utilise a distributed operating system Instead we maintain an operating system neutral stance and define a minimal set of changes and requirements In this section we propose a service architecture for the distributed system The following sections detail the implementation requirements and changes necessary for each service A concluding section provides a dynamic picture of how the system handles events of significance to composition 3 1 1 Distributed Agreement Construction of a distributed system relies upon there being agreement between computer systems This is to facilitate communication and to coordinate tasks involving multiple systems In the context of our work a common device abstraction is required as is agreement on the process of composition and to configure access to devices to or from other systems The extent of such agreement varies and may be realised at differing levels in the software stack At one extreme is the comprehensive in dictating a distributed operating system where every computer system runs the same kernel Because of the homogeneity all distributed services are guaranteed to be present on all systems This makes communication straightforward since it can be defined once and applied across all systems A middle ground stance is possible where
115. acktracking facility built into the Prolog runtime environment This however requires careful management in terms of when it is engaged during the process and when its use is inhibited The process avoids making assumptions about the suitability of devices being composed It does not presume a suitable match can be found or that multiple devices will be required Our intention is to be flexible in terms of the process composing what it finds in a particular context At specific points we seek to improve efficiency by forcing the backtracker to continue the search for further solutions and at other points we place constraints on which avenues to pursue Point to engage backtracking Exhaustive searches are managed according to the problem domain This means that at distinct points in the match process backtracking is engaged to continue pursuing satisfaction The failure to meet a particular constraint acts as the trigger in the following circumstances refer back to the discussion under guiding the search 140 i where a selected request alternative is of a lower or equal priority than any existing match try another because there may be more than one alternative of suitable priority ii where a device fails to match to a request gt try a further device as the pool of those with resources available may consist of multiple devices iii where a DGroup fails to satisfy a RQGroup try another from the selected device as devices may consi
116. aining requests The computer system indicated by the shaded area is the one receiving the deployment and the boxed area represents services on remote systems Once established IO Resources is notified to check resource availability and notify other systems to do likewise They utilise their IO Resources service to perform the check Where devices are found with resources available matching is triggered and composition notified on the appointed system requester remote Eanes ta t remote create gt check_for_available_devices SP check_for_available_devices multicast nerform_match i See ae e g figure 3 10 requester create notes solid lines indicate sequences which occur whereas broken lines may happen depending on circumstances perform_match l 3 6 6 Requester Cancel A requester cancel event requires a teardown of a requester and specifically those aspects related to composition It also means systematic cancellation of all stored results involving 68 the requester across the distributed system The event happens when a requester is removed from a particular system and notification is passed through to the IO_Requesters support service The event sequence outlined in figure 3 11 covers tasks relevant to composition It begins with notification that a requester requires removal The computer system indicated by the shaded area is the one req
117. al Bluetooth 16450 16550 16650 16750 16850 16950 compatible broadband parallel port bi directional ECP 1 x compliant intelligent i o controllers i20 architecture specification 1 0 simple IEEE1284 controller target TV communication multiple serial satellite communication audio controllers generic modem controllers voice Hayes compatible modem 16450 16550 16650 16750 data GBIP IEEE488 1 2 ds DPIO modules smart card data acquisition 3 performance counters encryption decryption network amp computing en decryption amp signal processing communications synch time amp freq test measure controllers controllers entertainment en decryption management card figure 2 9 Peripheral Component Interconnect PCI Class Codes As a contrast the Universal Serial Bus USB interconnect allows devices to be connected or disconnected while a computer system is operational Hewlett Packard Intel et al 2011 specific functionality when determining the type of a device To permit such dynamism a distinction is drawn between generic and device USB uses the notion of a class to scope the manner with which a device communicates with the host system A class is defined as a group of devices which have attributes or services in common It is denoted by the use of a code defined and maintained by the authors of the USB specification Class groupings shown in figure 2 10 are
118. al Control We set out to attribute control to discrete elements beneath a whole device With an ability to capture such a description of logical control a requester could specify what it is capable of controlling Composition would determine which elements of a device correspond as open to being controlled Our approach avoids coming at describing logical control by attributing existing driver code interfaces to discrete elements Instead this is about uncovering the operation of a device in terms of articulating control requirements and the functionality being controlled A further aspect is to account for system resource requirements necessary for control at a finer granularity than a whole Decomposing control Decomposing control is about detailing how a device is directed to perform particular tasks HCI research has focussed on the relationship of devices as peripherals That is the device must be managed and communication controlled by a computer system Our concern is to characterise control in terms of which device elements direct and are directed all without reference to code interfaces A recent classification effort sought to categorise the dimensions of interaction with driver code and constructed a taxonomy of the extent to which a computer system s processor is involved in device related action Smotherman s account detailed in figure 4 7 extends understanding of aspects to control by expanding data handling and driver acce
119. al and digital to analog audio convertor used for recording plus playback of audio 159 3 M Audio Audiophile USB a stereo audio codec MIDI interface with digital IN OUT A detailed description of all three devices is provided in the preceding appendix B 1 3 The Distributed System Our distributed system is implemented using the language Prolog Events manipulate a database forming our implementation The implementation as diagrammed in figure B 1 and combined with figure B 2 shows the integration of the match process into event handling and how events drive composition across the distributed system The 6 dark coloured lozenges represent events systemConnect requesterCreate create requester devices with resources available on new system s eonfigure device Submit outlets from g x new requester _ 1 ee og oe a yes from E iae A PEE ENS igure all systems a 9 check requesters amp queue outlets i B 2 ee 1 for matching T Submit unsatisfied outlets lf Se ee 7 PEE ees devices cancel any requesters with recently match results cancelled matches involving requester s _Submit those outlets l m m m m yes An devices with matches involving cancelled requester devices with matches involving requesters from disconnected system requesters cancel any match results requesters cancel any involving device match results involving devi
120. alterable or fixed output selection set of connections select criteria 4 2 6 Non Functional Aspects Quantifying performance falls outside of functional considerations yet it is a factor in determining which device is more reliable Affording non functional aspects a place in device description would permit fine tuning of requests that seek particular functionality 89 Composition could then make a determination of which device candidate is likely to perform better In the case of block storage devices an ATA interconnect hard disk provides slower access times when compared to a solid state drive SSD They are readily distinguished by performance differences yet they present the same logical interface Western Digital Technologies 2010a Western Digital Technologies 2010b Articulating a range of factors outside of logical control includes indicating when faults are likely to occur as well as quantifying performance It extends to guidance regarding latency estimating completion times or providing a time frame before faults occur We look to ascribing properties to key device elements Passage of time and guarantees Providing performance guarantees is about quantifying device performance such as guidance regarding latency of elements and estimating time periods for task completion They remain inaccessible and if mentioned at all are presented for reference purposes in product literature This is the case when attempting to as
121. alternative a requester submits This allows a range of alternatives to be included and tried as those of a higher priority are unable to find satisfaction It also provides a means of reasoning on whether a new match has improved upon an existing match by comparing their respective rankings Additionally until the highest priority alternative is matched then a requester s external communication structure will continue to be submitted automatically for re matching An example of the use of our simple certainty scheme is a requester seeking audio codecs capable of analog to digital ADC and digital to analog DAC signal conversion The alternatives compositeRequests are presented as a list associated with an external access point outlet outlet Requester Outlet CompositeRQList ActiveCompRQ Status outlet requester1 outlet1 composite_rql 100 composite_rq2 75 inactive compositeRequest Requester CompositeRQ RequestList compositeRequest requester composite_rqi rq1 compositeRequest requester composite_rq2 rq2 rq3 The first is a combined request rq1 for ADC amp DAC to be located on the same Device and the second a backup request pair rq2 amp rq3 of ADC and DAC on different Devices Note that the first alternative is allocated a priority of 100 whereas the other only 75 representing some degree of compromise Checking Terms Establishing correspondence involves traversing the structural d
122. alue correspondence between terms 141 142 6 Conclusion 6 1 Accomplishments Our work is a comprehensive contribution to distributed systems and operating systems by providing i ataxonomy of device form and function leading to their structural description which is employed in ii a suite of system services which support the discovery configuration and composition of devices and iii the process of composition is implemented within an inference engine to match requests to device descriptions These accomplishments are summarised below and novel contributions to state of the art highlighted 6 1 1 System Services The first of our contributions is a suite of system services related to devices They are based on a model of the process for establishing access to them The significant stages of discovery configuration and composition comprise the services required to create a distributed system 1O_Discovery The IO Discovery service is responsible for achieving awareness of remote device functionality It is consulted as a system s response to device connections and to reconfigure the distributed system Device connections are styled to raise an event on a computer system IO Discovery is tasked with providing distributed awareness of them Services cooperate to resolve which computer system is assigned responsibility for a device Separately they account for requester arrival and departure on a computer system Each syste
123. anced A term data_format matched value uq us enum analog A term connection_establish matched value uq us enum hot_pluggable accept submatch match factor check 4 gt 2 M C SC term electrical M C SC term characteristics A term width matched value length mm 8 3 M C SC term physical_dimensions M C SC term physical_manifestation A term connector matched value uq us enum rca_connector rca_connector A term direction matched value ug us enum Loutput A term classification matched value uq us enum external accept submatch match factor check 8 gt 7 M C SC term structures M C SC term mechanical_structure A term device_boundary matched value system boolean true M C SC term relation M C SC term Logical_structure accept submatch match factor check 14 gt 9 M C SC term electrical_interface A term direction matched value uq us enum unidirectional A term logical_channels matched value system integer 2 A term model matched value uq us enum stream ccept submatch match factor check 4 gt 4 SC term link SC term primitives A term direction matched value uq us enum unidirectional A term logical_channels matched value system integer 2 A term signal_format matched value uq us enum digital A term model matched value uq us enum stream accept submatch match factor check 6 gt 4 M C SC term Link A term compression matched value
124. and their driver code require external resources or explicit intervention to operate which creates dependent relations within a computer system This service seeks to alleviate the constraints and reduce brittleness to the process of configuring a device Ours is a comprehensive approach that stipulates changes and requirements to enhance our capacity to dynamically construct distributed systems The aim of the IO_Configuration service is to accomplish configuring devices on the computer system to which they are assigned In doing so to also prepare devices to participate in composition across the distributed system 3 3 1 Tasks Performed by the O_Configuration Service Manage computer system resources A low level task performed by the IO_Configuration service is to manage the resources of a computer system The objective is to ensure a viable system configuration and that it remains fully operational in the face of dynamic device connections The resources concerned those a device requires to operate These include interrupts for signaling and system memory regions for access to control registers residing on the device A record of system resources is used during enumeration to fulfill requirements as each device is configured This task requires that overlaps be avoided and no duplicate allocations A record of availability is dynamically adjusted as devices connect or disconnect Setup driver code automatically Another of the tasks performed
125. anges to fully implement the 46 IO_Discovery service They impact a range of specifications the definition of key components and require protocols for distributed interaction between services running on computer systems The full raft of requirements are as follows vili changes to interconnect specifications e device connections are logically visible ix requirements of device descriptions e indicate whether a device is already assigned to a system dynamic x protocol definitions e determine which computer system is to be assigned responsibility for a device e enumerate the devices attached to a computer system e determine where composition is to be conducted xi system specific records to be maintained e devices assigned to a computer system dynamic e connections to other systems dynamic computer system selected to conduct composition dynamic xii changes to computer system specifications e service is embedded in a processing module amp an integral part of system software 3 2 3 Interconnect Specification Changes Device connections are logically visible Discovery is the primary means by which a computer system is assigned responsibility for device configuration To enable this to happen involves some form of connection signaling on the interconnects where a system is attached This service is required to interpret this signal as a connection or disconnection Within the distributed system we draw a distinction between conn
126. arameters with univ operator to check for existence then try stateAdjust goal Term stateAdjust Spec StateID SAH Mode V NewV Term insert new amp delete old state into or from database retract state Element StateID V assert state Element StateID NewV executeStateAdjust Mode Element Spec SAT When trying the applyMatchWithDevice goal any leaf level annotations returned in the results are combined with the value correspondence to adjust state facts accordingly and the old value retained for later match removal applyMatchWithDevice Mode Match Requester Out Let CompRQ RQ RQGroup Device DGroup GMF SubMatch Match device _ Device DSpec _ applyDSubMatch Mode Device DSpec SubMatch applyDSubMatch Mode Device DSpec ATerm _ DS AV SMT applyStateUpdate Mode Device ATerm AV DS applyDSubMatch Mode Device DSpec SMT applyStateUpdate _ _ _ _ applyStateUpdate apply Device Term NewValue DSH _ retract state Device DSH OldValue assert state Device DSH OldValue shadowed retain old state value assert state Device DSH NewValue applyStateUpdate remove Device Term _ DSH _ retract state Device DSH RestoreValue shadowed retract state Device DSH OldValue restore old state value assert state Device DSH RestoreValue applyStateUpdate remove Device _ _ DSH _ state Device DSH Value 5 2 6 Match Conditions
127. arget 2 the sub goal find a request match is tried using a list of RQGroups associated with that request 3 the result returned must be non null a failed check results in backtracking to select another device to step 1 4 a satisfactory match is added to the results and the next request chosen 132 5 where unable to satisfy any request iteration ceases amp a null match returned for the alternative as a whole 6 furthermore any matches for requests tried earlier in the list are removed from devices bound to that point Matching request alternative goal The translation of search guidance generates a mid level goal detailed below attemptMatchUsingRQList _ _ CompRQ _ MatchList MatchList success return a non null list of matches for an alternative attemptMatchUsingRQList Requester Outlet CompRQ AvailableDeviceList RQH RQT MatchList X loop through list of requests associated with an alternative getRequesterSpec Requester Spec request Spec RQH RQGroupList Device must be part of the available pool member Device AvailableDeviceList with select Device amp group list from current request try to satisfy sub goal attemptMatchUsingRQGroupList Requester Outlet CompRQ RQH RQGroupList Device RQMatch match for a request cannot be null RQMatch CUT add match to list of matched requests attemptMatchUsingRQList Requester Out Let CompRQ AvailableDeviceList RQT RQMatch Match
128. art of a lower level goal refer to speculative application under the heading satisfying a request Matching requester s external access point goal The translation of search guidance generates an upper level goal detailed below and helper goals stated thereafter matchOut letToDevices Requester Outlet DeviceList any alternative to try is associated with the Requester s external access point outlet Requester Outlet CompRQPriorityList ActiveCompRQ _ getExistingMatchPriority ActiveCompRQ ActiveCompRQPriority member CompRQ CompRQPriority CompRQPriorityList current alternative must exceed priority of any pre existing match CompRQPriority gt ActiveCompRQPriority use request list from current alternative amp try to satisfy sub goal getRequesterSpec Requester Spec compositeRequest Spec CompRQ RQList attemptMatchUsingRQList Requester Outlet CompRQ DeviceList RQList CompRQMatch match returned cannot be null CompRQMatch cancel any pre existing match with Requester amp Device s cancelExistingCompRQMatch Requester Outlet ActiveCompRQ apply new match with Requester app LyCompRQMat chToRequester CompRQMatch determineOutletStatus CompRQPriority OStatus retract outlet Requester Outlet CompRQPriorityList _ _ retract outlet Requester Outlet CompRQPriorityList _ _ shadowed assert outlet Requester Outlet CompRQPriorityList CompRQ CompRQPriority OStatus
129. at A term sampling_rate matched value frequency hertz 48000 A term data_channels matched value system integer gt raj A term bit_resolution matched value system bit 16 accept submatch match factor check 9 gt 9 M C SC term function A term principal matched value uq us enum convert M C SC term role M C SC term task accept submatch match factor check 14 gt 14 M C SC term task element A term direction matched value ug us enum unidirectional A term logical_channels matched value system integer A term signal_format matched value ug us enum digital A term model matched value ug us enum strean accept submatch match factor check 6 gt 4 M C SC term Link A term compression matched value fug us enun uncompressed A term data_format matched value uq us enum pcm_audio accept submatch match factor check 6 gt 5 M C SC term chanhel M C SC term primitives accept submatch match factor check 12 gt 9 M C SC term comminications_Lin A term principal matched value uq us enum adjust M C SC term role C SC term task pr gShecking availability of Registration Unit analog audio_strean in available A term configure matched value uq us enum required C SC term approach SC term control ccf temm principal matched value uq us enum adjust CSi l C S term role A term data format matched value fug us enun digital A term
130. atched value frequency hertz 480001 A term data_channels matched value system integer t term bit resolution matched value syster bit 16 accept Submatth maten Factor check 3 M C s term function A term principal matched value uq us enum convert M c sC term Pole ne r g M C SC term task accept submatch match factor check 14 gt 14 M C SC term task element A term direction matched value ug us enum unidirectional A term logical_channels matched value system integer A term signal_format matched value uq us enum digital term model matched value ug us enum stream accept Submatch maleh factor ened M C SC term Link K term compression matched value fug us enum funconpressed A term data format matched value uq us enum pem_audio accept submatch match factor check 6 gt M C SC term channel M C SC term primitives accept submatch match factor check 12 gt 9 M C SC term comminications Link A term principal matched value uq us enum adjustJ M C SC term role M C SC term task 170 gt checking availability of Registration Unit audio_stream_in available A term configure matched value uq us enum required C SC term approach C SC term control A term data format matched value ug us enum Canalog A term conn ction_establish matched value ug us enum hot_pluggable accept submatch match factor check 3 gt 2 M C SC term electrical
131. ate to complete apply with Device green_2 us224_1 applying group match with Requester apply match with Requester white_4 requester2_1 MODE apply code adjust_dac_settings Request rql Request Group rqgroup1 gt DeviceCodeInterface dac_configure set_sample_rate set_resolution set_channels data audio_out_settings Request rql Request Group rqgroup1 bit_resolution system bit 16 data audio_out_settings Request rql Request Group rqgroup1 data_channels system integer 2 data audio_out_settings Request rql Request Group rqgroup1 sampling_rate frequency hertz 44100 asserting new match transaction done applying match with both Requester and Device s Requester white_4 requester2_1 Outlet outlet1 status flagged gt threshold gt MATCH PROCESS COMPLETED WATCH TRANSACTION 5 lt n es 8 a Requester white_4 requester2_1 gt Device green_2 us224_1 Outlet outlet1 Alternative composite_rqi Request rq1 Group rqgroup1 gt Device Group dgroup23 MF 28 163 Stage 2 Create Requester 1 The example continues with Requester 1 arriving on a further computer system This system then connects to the distributed system which initiates the match process again Stage 2 Match Expectations e process progressively works through satisfaction of Composite Requests involving a list of Requests that each consist of multiple RQGroups e unavailable resources registration unit on 1st Device ca
132. by this service is to setup driver code such that it is capable of configuring and controlling a device The critical dependency a device has upon driver code requires that it be made ready prior to making the device operational This involves extracting the driver code block from a device description and performing code translation to native processor code Configure devices for operation The principal task performed by this service is to configure a device for operation Introspecting the device description is necessary to ascertain the system resource requirements for a device Once these are provisioned driver code must also be readied The final aspect can only be accomplished using driver code A protocol for initialisation is defined that enables automated control of the driver to perform device configuration 3 3 2 Implementing the O_Configuration Service Our concern is to facilitate access to devices across a distributed system They must be configured however to make them operational once assigned to a computer system Within a context of computer systems being constructed out of independently deployed 53 components and defined by platform specifications this presents significant problems and requires an integrated set of changes To fully implement the IO Configuration service we are proposing changes to interconnect and computer system specifications a redefined set of key components including driver code and adding to the
133. certain access latency across storage devices of differing data persistence technology Fusion io 2008 Western Digital Technologies 2010a Western Digital Technologies 2010b Within the area of multimedia systems timing concerns are expressed as data bandwidth requirements for streaming video to from a device These may extend to referencing a continuous data rate for devices according to the quality of video frame and the rate of playback This can be viewed as an evaluation of device performance or a requirement of the system to provide minimum guarantees Hopper 1990 Barham Hayter et al 1994 Leslie McAuley et al 1996 Quality of service guarantees may also concern achieving particular data flow across a communications link Operating system support linking scheduling to an interconnect specific technique IP based over IEEE802 provides such for any device connecting Bavier Voigt et al 2002 Properties where articulated are about accounting for resource usage Bershad Savage et al 1995 Brown and Seltzer 1997 Banga Druschel et al 1999 An additional example is the Universal Driver Interface UDI which sets out to provide portable driver code irrespective of which operating system The specification defines a set of interfaces and semantics to be made available to all drivers within a runtime environment One of the interfaces provided is timer services designed to permit scheduling future events for handling via time
134. ces available e what a taxonomy and structural description can be derived to greatly expand the capacity to specify a sought after device use an agreed upon device abstraction that seeks to address the needs of multimedia amp distributed services and can be employed to frame a device description and formulate requests e how process steps are determined for satisfying requests and granting logical access to a device determine what constitutes satisfying a request determine how an arbitrary pool of devices can be composed link composition to granting logical access e when composition is conducted as a response to device connections to reconfigure a distributed system link device connections to events on a computer system provide distributed awareness for events on a computer system assign responsibility for device configuration to a computer system devices are configured for operation computer systems account for requester arrival amp departure 44 Between them the services introduced in this chapter cover where who and when The what and how have some of their requirements met too but they are discussed in subsequent chapters concerning a taxonomy and structural description of devices and the composition process In accordance with our model of the process the principal services concerned with building a distributed system are IO Discovery to handle the where and when and IO Configuration to deal with t
135. ces from disconnected destroy requester system destroy device requesterCancel remoteSystemDisconnect figure B 1 distributed system implementation activity related to connection events Starting the Distributed System To start the implementation involves e loading of the services responsible for supporting composition and e establishing an i o taxonomic database consisting of assertions detailing hierarchical relations between terms 160 In figure B 1 above the integration of the match process into event handling is shown Following on in figure B 2 below match process initiation is indicated by a dark lozenge Requester external access points outlets are placed in a queue and selected one at a time for participation in the match process The Prolog inference engine indicated by the perform match box evaluates which device from a pool of those with available resources is better able to satisfy the goal of matching against a request performMatch all systems check devices amp submit those with resources available perform match using queued requester outlet amp pool of devices does outlet have a pre existing match no requester cancels device s cancel old match result old match result device s appliy requester applies new match result new match result goto figure B 2 distributed system implementation activity related to the match process Connecting Devices and Add
136. cess Motivation A key capability we desire is to provide access at a finer granularity than a whole device and have the composition process handle arbitrating that access without the need for driver code to implement such functionality Also to permit a device to indicate the extent of possible access and have the process dynamically arbitrate then allocate such to requesters Illustrative example Returning to the example of an audio codec device our approach seeks to make it permissible to allocate audio in and out streams separately As such a request for the modules responsible for converting digital audio to an analog signal could still be matched and access granted despite having already allocated the modules to convert analog audio to a digital signal Technicals Resource availability determines whether the match process will be conducted The mechanism of denoting resource allocation is implemented through a branch level modules categories amp subcategories annotation of the structural descriptions associated with DGroups Each annotation represents a resource reference to an accompanying assertion recording its availability Collectively they are a dynamic picture of the extent to which a device s functionality has been allocated During the match process the availability of a resource is checked after verifying term correspondence but before deriving a sub match Where recorded as unavailable the term is rejected at that
137. ch removing shadowed state to complete apply with Device green_2 us224_1 applying group match with Requester apply match with Requester black_5 requester_1 MODE apply code adjust_adc_settings Request rq4 Request Group rqgroup3 gt DeviceCodeInterface adc_configure set_sample_rate set_resolution set_channels data audio_in_settings Request rq4 Request Group rqgroup3 bit_resolution system bit 16 data audio_in_settings Request rq4 Request Group rqgroup3 data_channels system integer 2 data audio_in_settings Request rq4 Request Group rqgroup3 sampling_rate frequency hertz 48000 asserting new match transaction done applying match with both Requester and Device s Requester black_5 requester_1 Outlet outleti status flagged gt partial gt MATCH PROCESS COMPLETED MATCH TRANSACTION 242 2 224 0 ee ate a ee a Requester white_4 requester2_1 gt Device green_2 us224_1 Outlet outlet1 Alternative composite_rqi Request rq1 Group rqgroup1 gt Device Group dgroup23 MF 28 Requester black_5 requester_1 gt Device green_2 us224_1 Outlet outlet1 Alternative composite_rq4 Request rq4 Group rqgroup3 gt Device Group dgroup22 MF 26 169 Stage 3 Connect 2nd Device Griffin iMic2 v2 The example continues with the Second Device a Griffin iMic v2 connecting to a further computer system This system then connects to the distributed system which initiates the
138. ch factor check 6 gt 4 M C SC term Link A term compression matched value uq us enum uncompressed A term data_format matched value uq us enum pcm_audio accept submatch match factor check 6 gt 5 M C SC term channel M C SC term primitives accept submatch match factor check 12 gt 9 M C SC term communications_Link A term data_format matched value uq us enum digital A term signal_mute matched value system boolean true M C SC term function A term principal matched value uq us enum Ladjust C term role C term task A term configure matched value uq us enum required A C C a M C M C term operate matched value uq us enum required term approach term control A term signal_ended matched value uq us enum unbalanced A term data_format matched value uq us enum analog A term connection_establish matched value uq us enum hot_pluggable accept submatch match factor check 4 gt 2 M C SC term electrical M C SC term characteristics A term direction matched value uq us enum input A term classification matched value uq us enum external A term device_boundary matched value system boolean true M C SC term relation M C SC term logical_structure A term direction matched value uq us enum input A term classification matched value uq us enum external A term device_boundary matched value system boolean true M C SC ter
139. ck to the device to update resource availability and the requester to configure access This event arises as the distributed system response to a positive change in device resources The event sequence outlined in figure 3 12 covers the preamble It begins with the IO Composition service receiving a perform match notification The computer system indicated by the shaded area is where matching is conducted and the boxed areas represent services on remote systems Once triggered IO Composition distributes notification to the 69 cluster of systems requiring them to check for unsatisfied requests As the IO Outlets support service on every system determines that requests are insufficiently satisfied they are submitted and queued perform_match local submit_unsatisfied_requests multicast z per request submit_available_devices Keo ph per device figure 3 12 perform m remote local remote multicast submit_device atch preamble notes solid lines indicate sequences which occur whereas broken lines may happen depending on circumstances This is followed by IO_ Composition distributing to submit device with resources available a further notification to all in the cluster The IO Resources service on every system performs a check and where they are available resources are submitted A request is selected and the process tries to f
140. composite_rq1 rql rqgroup1 audio_out_settings sampling_rate frequency hertz 44100 Goal expression The application of match results occurs where an alternative has been satisfied There are a series of goals that are used to traverse the result list and apply the match A significant sub goal applyMatchWithRequester processes annotations related to match parameters as follows applyMatchWithRequester Mode Match Requester Out Let CompRQ RQ RQGroup Device DGroup _ SubMatch Match getRequesterSpec Requester Spec applyRQSubMatch Mode Requester Spec Outlet CompRQ RQ RQGroup Device DGroup SubMatch applyRQSubMatch Mode Requester Spec Outlet CompRQ RQ RQGroup Device DGroup SMH SMT ATerm ODI DS AV SMH applyDateInterface Mode Requester Outlet CompRQ RQ RQGroup ODI ATerm AV applyDateInterface _ _ _ _ _ _ _ _ end of list or no ODI applyDateInterface Mode Requester Out Let CompRQ RQ RQGroup ODIH ODIT ATerm AV registerDataInterface Mode Requester Outlet CompRQ RQ RQGroup ODIH ATerm AV applyDateInterface Mode Requester Outlet CompRQ RQ RQGroup ODIT ATerm AV insert or delete match parameter into or from database registerDataInterface apply Requester Out let CompRQ RQ RQGroup ODInterface ATerm AV assert dataInterfaceTable Requester Out let CompRQ RQ RQGroup ODInterface ATerm AV registerDataInterface remove Requester O
141. connecting dynamically device initialisation involves key elements of a computer system For our purposes these elements consist of e devices defined earlier and including interconnect bridges e driver code is deployable software developed with the intention to configure and operate a specific device e kernel code is the section of an operating system that executes with security privileges and is responsible for resource management of a computer system it comprises services providing interprocess communication scheduling memory management and interrupt handling e platform configuration code refers to software embedded in a system platform with responsibility for performing bootstrapping it is tasked with establishing a viable logical configuration enumerating attached devices on known interconnects and using a fixed pool of drivers to configure those devices required to load an operating system 13 a system platform refers to a specification for a computer system consisting of a target processor and a suite of devices intended as a guide for developing an operating system e processor unit of general purpose code execution in a system implicitly includes memory e interconnect specification provides form and function underpinning for all devices that are developed to connect to a particular interconnect Although dependencies do exist between each of these system elements our concern is to narrow our treatment to
142. connection or disconnection The extent of computer system awareness is dependent on consideration of where the device was or is connected For an exclusive interconnect to which no other system is 47 attached the computer system concerned would be signaled through its interconnect bridge device Where two or more systems share an interconnect each receives a signal and they must collectively resolve who is to be assigned the device The protocol for resolving responsibility is detailed below Assigning responsibility results in a selective approach to notifying other systems of device connections based around relevance to composition The system assigned to handle device configuration is tasked with generating that distributed notification 3 2 4 Requirements of Device Descriptions Indicate whether a device is already assigned to a system dynamic The process of enumerating devices attached to an interconnect is about establishing whether they have already been assigned to another system This is involves probing the device to determine whether it has already been claimed by another system We require a device description to include an indication of whether responsibility has been assigned This status needs to reside on the device and be logically accessible by any system also attached to the shared interconnect It must be cleared as a device connects and be capable of being dynamically set when assigned to a computer system This is th
143. de having executed hence it must resort to performing its own device configuration across the entire tree The overall effect is duplication of responsibility most particularly code for loading an operating system and a suite of drivers each implementing limited functionality 4 Driver Code Dependency Upon Interconnect Specification A consequence of a device being designed to connect via an interconnect is the need for driver code to also be aware of the underlying specification This comprises definitions of logically visible structures It extends to how access to them is expressed and a functional description of the process of device control and communication We mentioned earlier that a device implementation embodies dependencies upon the interconnect With respect to driver code we can characterise its dependencies as comprising a distinct code block with interconnect awareness and another concerned with the functionality a device implements To illustrate the utility in drawing such a distinction we look at two devices of identical task functionality but interfacing to a computer system via differing connections A two dimensional mouse with a left and right button demonstrates the effect upon driver code of adopting a different connection interface In either instance the device adopts a communication protocol where multiple data bytes are sent containing change in X and Y coordinate position along with left and right button status One h
144. de system features related to processing or device functionality Alternatively connection topology may be influential or some other factor related to the physical environment e g across the same floor versus in another building Other than suggesting a range of possible factors any attempt to propose intricate policies for particular distributed scenarios remains outside the scope of our design We assume a candidate system can be determined from within a distributed cluster Finally a match re determination is expected when a system arrives or leaves In the process of determining where to match other systems are discovered beyond those adjacent These systems forming a match cluster are retained but only minimal routing information is kept A system is merely required to pass along communication to the next link 3 2 6 Records Maintained Devices assigned to a computer system dynamic Maintaining an accurate account of the topology of devices connected to each computer system is integral to being able to contribute them to participate in composition Physical connections can be represented by a tree an example appears in figure 3 3 A processing module defined later under the IO _ Configuration service form the root and the structure reflects the results of enumerating those devices attached directly to the processor s own interconnect and proceeding outward 50 Processing Module 1 bridge 2 other 3 4 bridge 5 6 7 other
145. derpin each transaction For instance a request to write is sent across the interconnect as a data packet Error free transmission is acknowledged immediately by hardware in a synchronous manner Later the receiver responds asynchronously by sending a separate packet back to confirm the data was written Hardware once again acknowledges successful transmission A contrast is provided by a Serial Mouse connected via a RS 232 C serial port to a computer system It transfers data as bytes generating a system interrupt per byte and is accessed via i o space USARSystems 1997 The communication link associated with the serial port utilises standard RS 232C signaling Furthermore the data transfer is at a set rate using an error correction protocol Signaling is half duplex meaning either the device or computer system are sending at any one time Internal links can be characterised in a similar manner to external connectors Consider an M Audio Audiophile USB audio codec control surface used for recording and playback of audio M Audio 2006 It comprises functionality for analog to digital and digital to analog audio conversion Internal links can be described by reference to the input signal characteristics of the respective codecs For the Digital Analog Converter it accepts digital audio sent as an isochronous stream that is a constant stream with no acknowledgement of receipt This stream may comprise stereo channels with each having a sample
146. dicate the user interface provided both physically their operation and perceptual requirements iii detail each of the exterior ports or connectors in physical terms and electrically iv where relevant insert communication links between other modules to provide details of data or signal format v providing further information on concerns at whole of device level like power consumption 99 As each module is detailed an indication is made of the links between them logical structure category Some of these may be deemed to require a communication link module inserted as an intermediary to detail data format or signals For a diagrammatic representation of this approach refer to the appendices where we provide a detailed analysis of three audio devices of varying complexity The example below is an illustration of how a description is expressed for a simple audio codec device similar to the Griffin iMic2 Griffin Technology 2010 The hierarchical structure relates to the taxonomy from which the terms are drawn The device description shown is expressed in the Prolog language as a list of lists The illustrative set of modules least indented terms are those that might be relevant to a requester seeking capabilities of an audio out signal for a pair of headphones task_element modulel task category function 1 subcategory direction uq us enum digital_to_analog aspect
147. differences exist between trying to access devices across a distributed system versus on a computer system For example the range of devices available may be reduced and limited functionality provided for distributed use Tackling this problem is relevant to using computers in the future The ability to access devices in a distributed context is becoming a significant factor in defining the experience of computer use We say this because the environment is already characterised by resources being spread throughout A plethora of computer systems and devices are present and capable of being connected together Satyanarayanan 2001 Considering contexts of future use the task of enabling access to devices is reliant upon a distributed system meeting the following requirements i a flexible capacity to describe sought after devices ii being made aware of devices in a context 111 responding to devices frequently coming and going iv ensuring devices are made operational v requests are matched to devices to grant access to them An example to motivate our focus on devices within a distributed system is that provided by building automation The scenario of home automation provides a context which is long lasting and involves dealing with devices to automate tasks The actual system outlined represents what is possible using existing technology 1 1 Home Automation Constructing a distributed system within a large contemporary home involves
148. distributed systems The result is that a series of issues and shortcomings were revealed at each stage In designing a new system these need to be addressed or accounted for and attention paid to the influential trends impacting distributed systems Additionally there is a need to improve robustness and to enhance flexibility as well as making composition more responsive We comprehensively target the shortcomings by addressing each one below Where a need is identified an improved approach is proposed Alternatively mention is made of the breakthrough required Collectively these points represent the technical requirements of a distributed system that would meet our stated goal of a capacity for it to endure 1 automate the process of establishing access to devices this would address a shortcoming and the trends dictate greater responsiveness 2 expand awareness of the context extending from events on a computer system through to the environment this overcomes the issue of transparency precluding context awareness amp addresses unreliability stemming from isolating the process of composition it also targets the trend towards greater interaction with the environment 3 adopt a more flexible approach to linking computer systems to form a distributed system addresses the issue of the discovery stage being overly reliant upon a specific interconnect 4 devise means of alleviating the key device dependencies comprehensive appro
149. e Mode Match Requester Outlet CompRQ RQ RQGroup Device DGroup GMF SubMatch Match device _ Device DSpec _ applyDSubMatch Mode Device DSpec SubMatch applyDSubMatch _ _ _ applyDSubMatch Mode Device DSpec SMH SMT _ _ _ DSA _ DRU SubMatch SMH executeStateAdjust Mode Device DSpec DSA executeRegistrationUnitAdjust Mode Device DRU applyDSubMatch Mode Device DSpec SubMatch applyDSubMatch Mode Device DSpec SMT applyDSubMatch Mode Device DSpec SMH SMT ATerm _ DS AV SMH applyStateUpdate Mode Device ATerm AV DS applyDSubMatch Mode Device DSpec SMT Note executeStateAdjust executeRegistrationUnitAdjust amp applyStateUpdate goals were all described earlier in the process enhancements section Speculative application of results A drawback to structural matching using our approach is that the process will satisfy successive copies of a request by matching to the same elements of a device Consider an audio control surface device that has a number of allocatable audio channel strips consisting of a fader buttons and lights as indicated in figure 5 1 TEAC 2007b MUTI m a O mme Tomm osez C LED amp switch a a fa om E REg o o 6 6 MlA AA S O E nri a we o 0 lu pi seLecT REC amp SELECT S S S Sls rt O LEDs A WOOO OVoO e e i el ae oli 0 om x Z REC amp SELECT ojo o o j E i switch SSE EE
150. e Network Device Mobile Handheld Device Home Infrastructure Device Across all categories are 12 device classes e Digital Media Server Player Renderer Controller Printer e Mobile Digital Media Server Player Controller Uploader Downloader e Mobile Network Connectivity Function amp e Media Interoperability Unit The class names specify functional capabilities and are the level at which DLNA certification is granted for audiovisual equipment Characterising Devices as Services A series of projects express device functionality as services Although they adopt a similar approach whereby service interfaces are requestable and not the device itself they differ in the abstraction used A Jini system consists of service providers inclusive of devices making resources as services available Sun Microsystems 2003 There may be more than one service implemented by a device Requesters referred to as clients make use of them through a lookup service acting as a broker trader locator for a distributed system All participants are object oriented hence of a particular class and utilise method invocations for remote communication Middleware services are written in Java as are the participants Newmarch 2006 In cases where a client is requesting a device service and is not aware of an assigned service code then a type must be specified This is a list of classes meant to 34 represent service interfaces A list of
151. e SBP 2 serial bus protocol 2 PC Card Graphics PCI and AGP includes high level graphics rendering services no device interfaces HID human interface devices includes game devices audio some displays uninterruptible power supplies VO Kit used to obtain path in dev folder Network then device file access instead SCSI Architecture Model ial supports SCSI primary commands SCSI Parallel plus SCSI USB generic USB devices only figure 2 12 Apple I O Kit Device Families By organising the framework around an architecture for a current platform the families mirror the device types used in such systems Reference to type is family dependent however expression is based around identifying codes extracted from hardware Interconnects are referenced by name strings and devices by numerical codes particular to an interconnect specification For example driver code for a device connecting via PCI has identity expressed in terms of the interconnect meaning the use of the string PCT to denote which interconnect and PCI specific class codes along with vendor and product codes to denote which device Apple 2007 31 Another operating system Microsoft s Windows XP Vista 7 is targeted at the Intel Architecture IA 32 and x64 system platforms The Windows Driver Kit WDK is the device driver development environment supplied It is designed to support layering where devices are serviced by severa
152. e Stage 2 create Requester 1 e Stage 3 connect Device 2 e Stage 4 connect Device 3 Each stage presents a transcript of the response generated by the distributed system A summary of the significant operations provides guidance B 1 2 The Participants Requester Two Requester Two has a single external access point where a request is seeking minimal features related to an audio processing task Specifically compact disc quality digital audio two channels of 44100Hz sample rate at 16 bit sample resolution to be converted for playback through line level output ports Where compromise is required just the core audio processing task is sought A request for the device functionality indicated above is framed with request alternatives in the following order iv single request e TaskElement Digital to Analog Convertor e ElectricalInterface AnalogOut using RCA jacks v single request e TaskElement Digital to Analog Convertor Requester One Requester One has an external access point where a request is seeking features related to two separate audio processing tasks Specifically better than compact disc quality digital audio two channels of 48000Hz sample rate at 16 bit sample resolution to be converted 158 for playback through line level output ports Additionally conversion of signals from line level input ports to the same quality of digital audio Initially the request is styled to seek all the audio features on th
153. e accomplishing this by identifying elements of discrete functionality and avoiding typing at a courser level 73 Benefits to removal and usefulness to composition Identification at a finer granularity affects not only the size of what is being requested but also the functionality being accessed We would be able to break the link between requesting a whole to gain access to aspects of a device Rather than the brittleness of matches returning access to all or nothing the process could accommodate requests formulated for elemental level access It would permit multiple requesters to access differing sections of a device 4 1 2 Assigning Types to Code Interfaces Overview of the restriction An alternate approach to device typing is assigning them to code interfaces The names used to distinguish which interface represent abstractions of functionality away from hardware Typically they are expressed as services and become the requestable entity not the device itself Our examination of device description revealed services differ in the abstractions used Edwards Newman et al 2002 Johanson Fox et al 2002 Sun Microsystems 2003 Cheshire and Steinberg 2005 Dong Hussain et al 2013 Additionally names are used to type content where requesters are required to understand names for profiles that represent general behaviours a device employs to communicate e g streaming audio from a media source to sink Bluetooth SIG 2009 How to
154. e configuration and composition we would like to provide a logically visible indication of system resource requirements and device resource availability along with mapping code interfaces to descriptions of elements from a device We intend for a requester to ask for device related functionality and through composition to have driver code interfaces returned that correspond This section is about building the expression of structural types for devices We discuss the requirements of typing in a distributed system before detailing logical expression of a device using the taxonomy We elaborate on capturing functionality in modules and motivate the need to associate elements of a description together rather than a single expression of the whole To conclude we discuss what constitutes an equivalent device using this approach to typing 4 4 1 Structural Typing in a Distributed System In a distributed system significant problems arise in circumstances where independent extensibility is permitted This is characterised by hardware and software being developed independently and deployed separately Meijer and Szyperski 2002 Taking a structural approach to device typing means multiple terms used to populate a structural description must be defined and hierarchically related in a type dictionary In the circumstances mentioned prior agreement must have been achieved on which type dictionary to use or else the system simply wont work Connor 1990
155. e copies and send them to all receivers having joined a particular group 2 2 2 Shortcomings in Distributed Awareness Disseminating awareness is necessary for dynamic construction of a distributed system The examples presented however point to shortcomings in how existing approaches handle discovery A range of factors impact the flexibility and responsiveness of these systems These consist of the choice of interconnect used for networking particular software layers the treatment of locality and an absence of distributed agreement Each of these are discussed in turn Assumed use of networking technology Current work operates under an assumption that a specific interconnect is to be used for networking computer systems and devices together Others have observed near uniformity to the use of Ethernet IEEE802 as the interconnect for a distributed system Kindberg and Fox 2002 Additionally this has seen widespread requirement for additional system software to implement networking namely TCP IP A lack of diversity has resulted in the process itself being scoped by the capabilities of the interconnect Most particularly discovery by using multicast on an IP subnet on top of IEEE802 The gaining of awareness becomes framed in terms of the steps associated with a functional description of the IEEE802 interconnect IEEE 2001 This would be of little concern if it provided all that a distributed system requires but it does not The remaining
156. e description is a request which is expressed as a logical structure using the same building blocks as a device description In the sections which follow we use the three stage model of the process to analyse existing work and identify issues that arise within a distributed context 2 2 Discovery Significance to a distributed system The intent behind a discovery step is to disseminate awareness of device functionality across a distributed system This means advising remote computer systems where requesters representing software that is seeking access to a device are located It may also be about advising other systems of requests requiring satisfaction By advising we mean disseminating notifications which are generated by services on a computer system to disseminate record that an event happened This takes the form of a message sent from a computer system to others in a distributed system An event is defined as being generated by services on a computer system and typically arises as a response to hardware signaling A service is a software unit that is a discrete part of an operating system It provides an interface that other software can access to perform tasks Acquiring and retaining awareness is a pre condition for participation in composition Without it reasoning on the validity of communication links is not possible This is because discovery is an important aspect of how connection or arrival events are handled on a computer syst
157. e first of a series of requirements that distributed services place upon a device description The derivation of such in the next chapter draws upon these to tailor composition for devices in a distributed system 3 2 5 Protocol Definitions Determine which computer system is to be assigned responsibility for a device This service provides the role of managing a sphere of devices for which the computer system is responsible An initial accounting of those attached is conducted once a system is powered on Adjustments to the sphere are accomplished through connection signals resolving as devices leaving or arriving The process of interpreting connection signals is discussed prior to looking at the construction an initial sphere Once a signal is raised on an interconnect the IO Discovery service proceeds to resolve this as a system or device either leaving or arriving It is possible for signals to be raised on any interconnect for which a particular system has an interconnect bridge attached Establishing what happened begins with a probe of the interconnect concerned Where device arrival is indicated a check is made to determine whether it is already claimed by another system If not determining whether a new device is joining involves checking system records for whether other systems are present Where an interconnect is shared multiple systems must negotiate device assignment according to a reliable distributed decision making policy Lampor
158. e level e fora leaf term L1 term name is used to create a device term to check for its existence L2 quantitative correspondence between values determined failure on either results in a null sub match L3 calculate acceptance measure L4 add leaf term plus annotations to results before selecting next term at the same level Matching RQGroup goal The translation of the search guidance generates a low level goal detailed below and helper goals stated thereafter The steps specified above B1 B7 L1 L4 are indicated at the relevant point in the goal matchRQGroupWithDGroup Requester RQGroup Device DGroup GMatch GMF create start term for group getRequesterSpec Requester Spec requestGroup Spec RQGroup _ AcceptGMF RQGModuleList device _ Device DSpec _ atom_concat DSpec _ A1 atom_concat A1 DGroup StartTerm with start term systematically check correspondence with device group walkRQGroup Requester Device StartTerm RQGModuleList GMatch GMF CUT check for match reaching acceptance value for request group GMF gt AcceptGMF WalkRQGroup _ _ _ NewMatch NewMatch NewMF NewMF All levels return match result once list exhausted WalkRQGroup Requester Device OldTerm RQGH RQGT Match X MF Y MODULES CATEGORIES SUBCATEGORIES loop through list amp try terms at current level RQGH RQTermName RQMC RQSA RQOCI RQMF RQSubSpec 137 use request term name with univ
159. e of equivalent functionality The published datasheet for a Texas Instruments PCM2900 single chip USB stereo audio codec Texas Instruments 2007 contains a thorough account of form and function which we will use to expand the device s description A summary of key elements of referred to in building a structural account appears below 147 Device Structure a series of groups each comprising a range of modules group 1 General G task element TE type control source 2 Digital to Analog Converter DAC convert USB control 2 DAC MuteOut adjust USB control 2 DAC Line Out Volume adjust USB control 3 Analog to Digital Converter ADC convert USB control 3 ADC Gain adjust MIC LINE switch 4 Audio Stream IN OUT transform n a 4 USB IN OUT director n a 4 USB Control transform n a user interface UI 3 MIC LINE Switch toggle MIC or LINE setting communication link CL 2 Digital OUT to DAC 2 s complement PCM 2 Analog OUT from DAC 3 Digital IN from ADC 2 s complement PCM 3 Analog IN to ADC 4 USB Isochronous IN OUT electrical interface EI 2 Audio OUT 3 Audio IN 4 USB Port 3 5mm stereo jack 3 5mm stereo jack cable connect type A connector Device Code Interfaces DCI ADC DAC DAC mute DAC volume Registration Units RU Audio Stream In Audio Stream Out Device State initial values ADC DAC DAC Volume Left DAC Volume Right DAC Mute select sample rate resolution channels select sample rate resoluti
160. e proposals for home automation frameworks refer to the Aware Home Android Home amp C Bus Automation System Abowd Bobick et al 2002 Clipsal_Integrated_Systems 2005 Isaac 2011 The setup used extends beyond mere customisation of user interfaces to nailing down a fixed configuration for the entire system ensuring control units are made aware of target devices and the set of operations they perform Upon closer examination home automation is made possible by three factors underpinning the system i the range of devices must be determined before installation the capacity to describe devices is bounded ii all setup performed manually awareness of devices is fixed no further devices can be brought inside amp all devices are configured at installation iii agreement has to be present at comparable levels of software on all systems control units are setup for access to set devices there is no matching step These factors mean the system fails to meet the access requirements stated earlier for ensuring future use and it will not work today unless all three have been observed The challenge is to devise ways of meeting these access requirements and to provide a robust but more flexible and responsive distributed system Our research in the area of operating systems and distributed systems sets out to investigate provisioning access to devices across a distributed system We take up the challenge and look to building a capacit
161. e same device Where compromise is required then to try all features but divided into separate tasks on different devices As the need to compromise is increased try less features on different devices The last option is to try firstly one task with less features then the other A request for the device functionality indicated is framed with request alternatives in the following order TaskElement TE ElectricalInterface EI CommunicationsLink CL i two separate requests on the same device 1 e TE Analog to Digital Convertor e TE ADCMute e EI AnalogInRCA e CL DigitalAudio 2 e TE Digital to Analog Convertor e FI AnalogOutRCA e CL DigitalAudio 11 two separate requests on different devices 1 e TE Analog to Digital Convertor e TE ADCMute e EI AnalogInRCA e CL DigitalAudio 2 e TE Digital to Analog Convertor e EI AnalogOutRCA e CL DigitalAudio iii two lesser requests on different devices 1 e TE Analog to Digital Convertor e CL DigitalAudio 2 e TE Digital to Analog Convertor e CL DigitalAudio iv single request e TE Analog to Digital Convertor e CL DigitalAudio v single request e TE Digital to Analog Convertor e CL DigitalAudio The Devices The three devices to be used in this example are 1 Tascam US 224 an audio control surface with stereo audio codec MIDI interfaces with digital IN OUT Griffin iMic2 v2 an analog to digit
162. eates uncertainty which needs to be dealt with in three areas From being able to verify term existence with a device to rejecting trivial structural matches and resolving which is the preferred request alternative Each of these is treated separately and the technique for resolving the problem outlined 115 Quantifying structural matches As results are constructed there is a need to distinguish meaningful from trivial matches Trivial in terms of being expressed as superficial elements of a device description satisfying a request in preference to more meaningful results We suggest superficial by virtue of branch terms being only minimally qualified by the presence of leaf terms in the results Additionally a module has greater qualitative worth where the sub structure has multiple branch terms matching at the same level Where branch terms correspond but there is minimal quantitative qualification at the leaf level we intend to reject the sub match Not only would removing these trivial cases be preferred but also for more subtle problem specific ones where key quantitative factors fail to correspond refer to later process enhancements section The motivation for a metric to measure the strength of structural correspondence arises from the importance of leaf level quantitative matches in generating meaningful results Particular terms are critical to describing the purpose of a module and qualifying the dimensions of sought after form and fu
163. ection signaling and notifications It is one of an expanding context and increasing abstraction from hardware Signaling relates to hardware raising an interrupt on an interconnect as a device connects disconnects Alternatively it may provide a logically visible means of detection by services running on a computer system Whereas notifications are generated by services for instructing other services to perform tasks related to device composition across a distributed system The construction of the distributed system is not restricted to having to use any existing network infrastructure We avoid mandating any underlying infrastructure to be used to link computer systems Instead we define the distributed system by the capacity for systems to communicate with each other which is made possible by systems having awareness of devices across multiple interconnects We do however require interconnects to raise system interrupts when devices connect or disconnect Their specification must detail the provisioning of hardware level connection signaling leading to interrupt generation Recent interconnects such as USB Anderson 2001 Intel 2002a and Firewire OpenHCI 2000 provide for a change in connection status on ports attached to an interconnect bridge An alternative is to express connection events in terms of polling or time leases similar to Jini leasing Waldo 1998 Either is acceptable as long as signaling occurs and is resolvable as a
164. ed for Linux USB drivers PCI Bus Device Support e Initalize PCI module Exploration of bus attached devices and drivers Device setup bus mastering enable disable Power Management related functions PCI memory pools consistent DMA mappings Configuration space access Functions for Linux backward compatibility drivers pci compatc Process Level Activities e Get pointer to current task structure this replaces the current macro e Add Remove a caller as process level worker e Initalize process module e Create kernel thread Scheduling Primitives kernel schedc Wait Queue List Manipulation kernel forkc V O Resource Management e Allocate Release I O port memory region e Release any resource e Check I O port memory region availability e Remap Unmap I O memory from kernel address space e Remap I O memory into kernel address space no cache Deferred Activities e Initalize Softirq Thread s Softirqs include linux interrupth softirqgs are multithreaded not serialized BH like activities Tasklets kernel softirqc amp include linux interrupth tasklets are multithreaded analogue of BHs differ from generic softirqs one tasklet is running only on one CPU simultaneously differs from BHs different tasklets may be run simultaneously on different CPUs Old style Bottom Halves and Task Queues kernel softirqc Time and Timer Implementation e Initialize Timer Thread Linu
165. eded button INPUT pressed 7 MONITOR status evaluate loopback control y Audio USB Stream IN OUT IN OUT TE TE ransform l USB Control USB TE Port D gt status USB LED Midi IN OUT ua ransform Interface IN OUT UI fader position UI channel fader slider button pressed U released channel MUTE switch channel SELECT switch on off ut channel MUTE LED channel RECord LED channel SELECT LED on off adjust XOR ADC Gain B on off signal threshold exceeded DAC Mixer v CL PCM audio DA y Mute DAC amp adjust_ convert y XOR on off CL CL midi relative position fader position button pressed released button pressed released on off u fader NULL LED SOLO LED BANK lt LED REW LED BANK gt LED F FWD LED PLAY LED RECORD LED midi audio output port coaxial S PDIF audio input port coaxial S PDIF channel SIGNAL LED input OverLoad LED TRIM level input potentiometer MIC LINE GUITAR input switch V LNdNI audio input port balanced XLR audio input port 1 4 Line Guitar unbalanced audio input port balanced XLR audio input port 1 4 Line Guitar unbalanced _ channel SIGNAL LED input OverLoad LED w TRIM level input potentiometer MIC LINE GUITAR input switch Line Out level potentiometer g EESE RE RA EEEE mE c LineOut Volume
166. efines the extent of flexibility built into the system Composition also relates to what is required to formulate a request and describe a device When the process is conducted defines responsiveness Where it happens could be interpreted as affecting both responsiveness and flexibility Scope of possibilities Being able to establish access to resources on other computer systems is integral to providing a distributed system Scoping of the process of composition responsible for achieving such is worthy of investigation and involves asking e how is satisfaction achieved during matching e who participates amp what is being matched e when is the process conducted e where is the process conducted in a distributed system Our focus divides the treatment of composition into two sections Firstly we examine how devices are described and requests framed Then to look at the broader distributed process through to establishing access 2 4 1 Describing Devices This section looks at the who and what of the process of composition by examining the abstractions adopted to describe devices Existing approaches are chosen from elements relevant to and select examples of distributed systems These range from descriptions of hardware operating system concepts through to characterising device functionality Describing Hardware Interface Description Languages IDL Interface Description Languages IDL specify a functional interface to a device a
167. eg i ia Touch Tablet iTouch Screen T E i i i S i i Sprung oO s i i i o a Treadmill Mouse Joystick 3D Trackball M Sls ry i i i Trackball i i Ferinstat i i iX Y Pad T g i i z Torque i i i Isometric s Sensor l i Joystick a f i t i rotary linear puck stylus finger stylus finger small fixed small fixed horizontal vertical location with twist figure 4 1 Buxton taxonomy of continuous manual input devices A shortcoming is that the domain is limited to continuous and hand controlled devices It ignores distinctions between discrete versus continuous input and makes no mention of the agent controlling the device Later research by Card et al uses morphological design space analysis to extend Buxton s work Card MacKinlay et al 1990 Card MacKinlay et al 1991 They set out to classify input devices as points in a parametrically described design space Their aim is to find abstractions for generating the space and test contained designs They see modeling device interaction as consisting of a i primitive movement vocabulary that gives the elementary sentences expressible in the human machine dialogue amp ii composition operators that provide methods of combining the vocabulary into a large set of combinations The result is a graphical representation as shown in figure 4 2 of the transformation between human action in the physical through mappings inherent in the device
168. em and the wider distributed system Determining which of these events are relevant will define the sort of responsiveness built into the system Scope of possibilities Providing access to resources on other computer systems is integral to providing a distributed system The scope for discovering these resources is reliant upon the way in which the process of composition is driven Also the level of integration between distributed software and the operating system on a computer system A range of semantics worth investigating consist of e what exactly is being discovered e how is awareness achieved of devices or requesters on other computer systems e how widespread is awareness within a distributed system e what happens upon receiving a distributed notification With a focus on discrete devices our concern is to ascertain how awareness of connections is achieved in a dynamic setting This is coupled with how requests are uncovered and acted upon 2 2 1 Achieving Remote Awareness A select set of distributed systems work illustrates existing approaches to discovery Each differs slightly in their handling of awareness Our examination of discovery is kept separate from composition Where middleware is referred to we think of this as a software layer that provides distributed transparency by defining protocols for communication between corresponding layers on computer systems It assumes a computer system has already been configured by an op
169. emaphore signaling scheme between the interconnect chipset and driver code so that either can signal events This happens separately for each packet transmit receive context and uses both a control register and status signaling on packet headers within the memory buffers OpenHCI 1997 17 24 The Firewire OHCI specification for accessing a bridge from a computer system also provides separate bit fields for notifying interrupts These can be masked as needed to ensure that checking does not happen till events have happened and status updated At the level of packet transmission Firewire not only guarantees that only one device will be transmitting as a result of arbitration for access but also provides the concept of a fairness interval This permits all devices attached to the interconnect to transmit exactly one packet during a set time period IEEE 1995b 35 36 Properties related to arbitration Groupings emerge from capturing the properties related to the differing granularity of these hardware based mechanisms for arbitrating access Arbitration becomes a significant category in a description of device elements in a similar way to control It extends to indicating how selection is made where multiple inputs or outputs exist Expressed as terms that characterise these properties the break down is e arbitration logical access command sets amp security access restriction alterable or fixed input serialisation serialisation policy
170. ements Devices A device is not described by a single structure rather a set of meaningful associations Utilising the concept of DGroups avoids searching an entire device for related modules We make use of the physicality of devices which allows us to describe structures as being in proximity to each other User interface elements have a physical manifestation to them which means they can be associated It is also possible to describe a signal path from or to a particular point and refer to them as being associated Because devices have this special status a request can target a DGroup and avoid having to widen the search 5 4 2 Match Process Optimisation A progressive narrowing of the search space happens as request alternatives are tried through to traversing modules The match process is more sophisticated than a simple module to module comparison of structural descriptions making up a request against those associated with a pool of devices For domain specific reasons we remove search options that are no longer relevant This happens dynamically as the search proceeds and has an 139 effect across all levels The search guidance provided by the requester underpins the reason for trimming the search space in the following circumstances i knockout devices the pool of devices participating is restricted to those having resources available to be accessed gt this is because there is no possibility of access to a device where resource
171. emory IOMMU processor local interconnect interconnect bridge primary interconnect i o device i o device interconnect bridge i o device secondary interconnect i o device i o device figure 3 5 computer system organisation incorporating a processing module There is an additional constraint that must be tackled involving device access to system memory by utilising an I O Memory Management Unit IOMMU The dependency concerns the need for it to be allocated memory regions We extend the definition of a processing module to incorporate an IOMMU which is to be managed by kernel code in conjunction with distributed services Service embedded in a processing module and an integral part of system software Contemporary systems perform their resource allocation in software This establishes a device dependency upon platform configuration and kernel code to reference logical requirements allocate resources then update device based structures We tackle both dependencies together and independently define services to handle the task The 57 IO Configuration service is tasked with ensuring devices attached to a computer system become operational It is the only low level code present prior to devices becoming operational and must complete its task to permit communication with external systems As such it is required to be present when the system is powered on Therefore this service is embedded with the
172. empting to map network location to the physical environment e g gaining access to the webpage for a printing device that is located where in the environment Presently this requires a manual configuration step prior and consequently forces aspects of the distributed system to act as fixed infrastructure Obtaining proactive knowledge of the environment is needed for applications to make use of context awareness through appropriate interfaces provided by the system Dependence upon external network infrastructure In choosing a style of communication where the sender of a message is unaware of who is receiving them existing systems have become dependent on an intermediary The use of multicasting is affected by network equipment principally routers which are non participants in composition and lack awareness of higher level distributed protocols The essential point is that the ability for messages to be sent or received between systems is not controllable by any of the participants or by software managing the distributed system This situation is the result of routers taking multicast registration from interested listeners and handling delivery of messages to them However the extent of and depth to the re transmission of messages is configured alongside the network infrastructure not the distributed system Removing this dependency upon equipment that must be statically configured is necessary to improve distributed system robustness and e
173. ence between structural descriptions accords with the structure of our taxonomy Terms become more specific at deeper levels and are quantified at the lowest level If we were to simply conduct the search by checking the range of modules within a structural description combined with the number of DGroups making up each device description then the number of comparisons creates a large and complex search space Exploring all the possibilities between a requester and a pool of devices has the potential for combinatorial explosion The basic search strategy alone is not equipped to combat this danger Accordingly the problem is tackled in the way we structure requests and devices in combination with how guidance is provided to the search and management of the backtracking facility 5 4 1 By Structuring Requests and Devices Before the match process has even begun we structure the participants to reduce the initial search requirements thereby avoiding the need to search every module from every structural description Search space reduction is facilitated by virtue of how requests are expressed and devices structured Requests When formulating a request describing an entire device is not required Only those elements deemed relevant need to be articulated That is the responsibility for determining which sections relate to facilitating access rests with the requester as does the choice of which details are pertinent to matching particular device el
174. ences to the operating system are not dynamically composed that have already been statically resolved at development time The inherent awareness of the semantics and syntax of services is evidence of their tight integration into the kernel The extent of compliance includes adopting the kernel s security model in terms of memory and input output access along with interrupt signaling This extends to the execution model defining the extent of arbitrated access to and the dynamic picture of what driver code looks like to the rest of the system It encompasses how driver code references external software be they to elements of the kernel or other software There is little variance to the pattern across commercial operating systems Some effort has been expended to tackle the knowledge required for code development through incorporation of driver requirements in object oriented code libraries as in Apple s I O Kit Apple 2007 This enables key details to be implemented within a system library pertaining to interfacing with the kernel and reduces the steps to be undertaken when developing a driver for that particular operating system It accomplishes hiding the complexity but in no way tackles removal of the dependency A clearer illustration of the extent of engineering required is that of the Device Driver Environment DDE provided for the L4 operating system to permit drivers targeted at the Linux kernel to execute in a different context Helmuth
175. ension to a set of interfaces and access mechanisms for particular device hardware The dependency is for configuration and operation in compliance with a standard that establishes a distinct type around features common to more than one device The PCI to Firewire bridge cited above is Open Host Controller Interface OHCI compliant and can be managed by a driver targeted at that specification In this case additional features implemented by the bridge are simply not recognised and hence not logically accessible refer to Firewire OHCI 1 1 specification OpenHCI 2000 Texas Instruments 2003 For device specific drivers coverage expands beyond interconnect specified structures and any standardised interfaces to those features implemented by a particular device The dependency is for tailored configuration and operation A pertinent example is a Matrox G400 AGP interconnect based graphics adapter implementing a PowerMode suite of features in addition to the Video Graphics Array VGA standard A driver with full awareness is needed for the device to exhibit any functionality beyond VGA compatibility Matrox Graphics 1999 2 Device Dependency Upon Interconnect Specification An interconnect specification defines logical interfaces to facilitate reference by an interconnect bridge driver A device implements these structures to provide an indication of its particular type and which system resources are required e g interrupt signaling memory
176. equirement is to ensure every RQGroup is sufficiently matched What is needed is for every RQGroup in the list to bind to a DGroup and be matched 110 iv Satisfying a RQGroup The structural descriptions associated with a RQGroup and a DGroup will correspond unpredictably Without guidance it is possible for a correspondence check to return a trivial result For the moment trivial is to be regarded as upper branch matches appearing in the results but with the lower level consisting of the most minimal of sub matches The requirement is to ensure acceptable correspondence between structural descriptions What is needed is a measure of acceptance to be used as an annotation throughout a structural description associated with a RQGroup Furthermore to annotate where a summation of measures for a sub match must reach an acceptance threshold to include a sub match in the results A deeper treatment of this concept appears in the next chapter under the section dealing with uncertainty 111 112 5 Composition Within the distributed system composition is handled by services running on each computer system Requesters and devices participate in a match process conducted on a computer system that may be remote to either or both of them Once a request is satisfied the results are returned to both participants for application thereby configuring access and updating resource availability We develop a knowledge based system comprising 1 a
177. er adjust pool temperature or turn off games console Separate from these units are wall mounted keypads in each room providing button controls over the lights and buttons assigned to custom functions Motion detectors are used in rooms to detect occupants and adjust lights Weather sensors automatically switch on lights and thermostats permit temperature control Surveillance cameras mounted strategically throughout the house deliver pictures directly to a selected display An on screen avatar reports visitors ringing a doorbell on the front door Further automation tasks include remote control of the shower according to individual presets e g temperature or to start filling a bath The server is utilised to store access and selectively distribute music videos and television channels It is also possible to browse and share photos that are stored centrally The system provides Internet access permitting the streaming of online videos and viewing of websites on any display screen It is even possible to view security cameras and interact with the control software when remote to the house e g to manage the temperature turn lights on before returning or set the timer on a video recorder The system uses a photo of each room as a control template where lights may be switched window shades altered or audio video components switched on off all by touching that item in the image All of the equipment be they server mobile or audiovisual compo
178. er to NeXTSTEP OS code development NeXT 1993 Alternatively when loaded into memory at run time to execute code by translating from a virtual processor definition refer to Taos VPAsm Taos 1994 or to compile to an intermediate form then to native code for execution refer to LLVM definition Lattner and Adve 2010 Lastly when code is scheduled to run to translate from code targeted at an alternate processor as each block is executed refer to the appendix on Rosetta Apple 2009b Although means of alleviation exist the role performed by a driver precludes their use The reason is related to its dependency upon kernel code Drivers may require access to privileged or system instructions of the processor e g invalidating cache entries as part of memory management or have the processor be executing in the same security mode as the kernel e g updating the processor on the location of page tables being a privileged operation As such existing approaches resort to operating system guidelines provided with their development environment and compile drivers for a specific processor architecture as in I O Kit Apple 2009a 7 Device Dependency Upon Kernel Code By definition a device relates to kernel code through its driver since it alone is aware of the specifics and can readily interface with the kernel This would seem to preclude the possibility of a dependency however the need to perform configuration as a result of dynamic connec
179. er_1 MODE apply code adjust_dac_settings Request rq5 Request Group rqgroup4 gt DeviceCodeInterface dac_configure set_sample_rate set_resolution set_channels data audio_out_settings Request rq5 Request Group rqgroup4 bit_resolution system bit 16 data audio_out_settings Request rq5 Request Group rqgroup4 data_channels system integer 2 data audio_out_settings Request rq5 Request Group rqgroup4 sampling_rate frequency hertz 48000 asserting new match transaction removing shadowed state to complete apply with Device red_1 imic2_1 applying group match with Requester apply match with Requester black_5 requester_1 MODE apply code adjust_adc_settings Request rq4 Request Group rqgroup3 gt DeviceCodeInterface adc_configure set_sample_rate set_resolution set_channels data audio_in_settings Request rq4 Request Group rqgroup3 bit_resolution system bit 16 data audio_in_settings Request rq4 Request Group rqgroup3 data_channels system integer 2 data audio_in_settings Request rgq4 Request Group rqgroup3 sampling_rate frequency hertz 48000 asserting new match transaction done applying match with both Requester and Device s Requester black_5 requester_1 Outlet outlet1 status flagged gt partial gt MATCH PROCESS COMPLETED MATCH TRANSACTION Requester white_4 requester2_1 gt Device green_2 us224_1 Outlet outlet1 Alter
180. erating system Publish Subscribe A Jini system consists of service providers which include devices and clients which make use of them Waldo 1998 Arnold 1999 Sun Microsystems 2000 The middleware is written in Java with clients and services constrained to have their interfaces expressed similarly Discovery defines the way a device service becomes part of a group federation Then there is lookup which reflects the current members and acts as way of finding services The separate process approach is referred to as publish subscribe Locating a look up service is the initial task for both services and clients This service is a specialised part of the Jini system It is started independently to the process of discovery typically during system initialisation It is responsible for taking device service registrations matching client requests and responding to these requests by listening on a reserved port Devices and clients use network announcements either multicasting messages where a lookup service is unknown or unicasting to make contact outside of a local network but at a known address Jini relies upon a properly configured IP networking layer in system software which implies Ethernet IEEE802 is the interconnect and an HTTP server to underpin execution of services The iRoom interactive spaces is middleware that provides event based communication through an intermediary which handles a variant of the publish subscribe approach
181. eration performed on either requester or device The retention of results facilitates providing a responsive and flexible distributed system by ensuring that when disconnections happen it 114 is possible to recover from a fault This can be accomplished by removing access via cancellation of matches and conducting composition to reconfigure Structuring the results A match result concerns a single RQGroup and DGroup and provides an indication of where correspondence was found between them As such results are expressed at that granularity based on a structural description The only differences are that both branch and leaf terms have annotations included from both participants and leaf level values represent an indication of the quantitative correspondence found not properties of a participant All these inclusions are necessary to accommodate removing a match later and on a different system from where match was conducted Whether applying or removing a match with devices or a requester it is a matter of traversing the same structure but treating the annotations differently e g resource availability is relevant to a device whereas code interfaces pertain to a requester The implementation builds match results as correspondence is derived during the traversal of a RQGroup s structural description Once the result has been applied with either participant it is asserted as a fact in the database and an accompanying header included to identi
182. erform the task of emulating a system platform including devices by providing a guest operating system with the illusion of access to actual hardware Whitaker Shaw et al 2002 As such hardware functionality is articulated in software requiring an account of both logically accessible and implied aspects of devices Sugerman Venkitachalam et al 2001 Barham Dragovic et al 2003 Garfinkel Rosenblum et al 2003 Despite such properties being articulated in the VMM they remain implied for composition since virtual devices are matched with guest software requests using named types How to overcome these restrictions Our proposal is to articulate the properties that are implicitly associated with named types Then to make these properties integral to the specification of device type This task is to be accomplished through a structured breakdown of devices into elements of form and function In accordance with the discussion so far we suggest adopting a minimal abstraction of hardware This has the advantage of enabling us to draw upon the physicalness of devices a point also raised in the previous section That is they are manifest in the environment present an explicit interface to it and their functionality is implemented by physically discernible elements Benefits to removal and usefulness to composition Articulating the full range of device properties and granting them logical visibility through incorporation into the expres
183. escription associated with a request and checking with the device at each point It is no mere tree walk for reasons of the need to confirm a term even exists then the possibility of multiple instances of same term at any level The first step in deriving correspondence is to check a term exists This is accomplished by reference to both the request and device The utility in this approach is that it enables checking without requiring the process to have knowledge of the actual terms just the hierarchical structure Consequently we are able to keep the definition of taxonomic terms separate from the search process The way in which the process checks that a specific point corresponds is to dynamically create a new Prolog language clause using the univ predicate Then to reference the clause as a goal in the matching rule Stating as a goal actually performs a check of the database for the existence of the clause as a device fact Success with binding constitutes finding correspondence The components for constructed clause stated as a goal RQTermName OldTerm NewTerm are drawn from the following sources 117 a the functor RQTermName is supplied by the RQGroup specifically the terms from its structural description b the first argument OldTerm is a string concatenation drawn from the DGroup s structural description Prior to traversal a starter term is crafted to identify the particular device and DGroup being checked dev
184. ese are captured in data structures that are conceptually bound to an interconnect s expression of resources and locality For instance Firewire uses a register NODE IDS to denote locality in terms of interconnects bus ID 10 bits amp local ID 6 bits IEEE 1999 IEEE 2000 whereas PCI devices have locality specified in a register CONFIG ADDRESS coded to include device sub functions bus 8 bits device 5 bits amp function 3 bits PCI SIG 2002 Singularity represents an operating system approach to declaring system resources required by a driver at run time and automating system resource configuration It uses a manifest presented as metadata to accompany driver code In the manifest system resources are declared using hardware references to terms such as registers ports interrupt request lines and memory Hunt and Larus 2007 Indicating device state State is representative of the internal workings of a device expressed as discrete values These logical structures reside on the device and are to be distinguished from driver code s use of data variables A complex example is USB devices that can be in several possible states some visible across the interconnect and others private The specification indicates that establishing state relates to initialisation requirements power usage operability connection events and reset notifications As such it involves awareness of possible transitions from one state to another whic
185. ess these issues by utilising properties as measurable descriptors and any explicit use of absolute factors is avoided by not referring to whole devices by using named types Establishing the ability to compare device features is possible by virtue of properties being quantitative 4 3 2 Structurally Relating Terms Properties as Categories and SubCategories During the derivation of properties we discussed description in terms of properties For the purposes of our classification effort we shall start by referring to properties as categories in the taxonomy Where qualification is needed to describe a particular category terms will be introduced and used as sub categories For instance the category physical manifestation is too broad and splits into physical dimensions and physical weight Aspects and Aspect Values Beyond the use of sub categories describing categories a further expansion is needed but for different reasons Particular properties have greater utility through being measured quantitatively e g length 3metres These lowest level terms come about by each sub category being further qualified by having a set of what we term aspects associated with them For each aspect there is an aspect value associated with them to quantify the descriptive term They are expressed using the current international standard metric system the International System of Units and elaborated upon in the next chapter under match process enhancement
186. ess to system memory Devices employing Direct Memory Access DMA however utilise purely physical addresses which raise security concerns since their effects cannot be isolated Recent efforts to address this issue have employed an I O Memory Management Unit IOMMU to manage device access to system memory Intel 2008 Advanced Micro Devices 2009 Typically this is situated in a processor interconnect bridge device it translates addresses from device requests into system memory addresses and checks appropriate permissions on each access The kernel is required to assign each device a protection domain with the IOMMU As such a dependent relation emerges for supply of memory regions in order to make use of device related memory management units 8 Device Dependency Upon Processor Our investigation of dependencies has established that driver code executes upon and is sensitive to particulars of the processor whereas devices are linked to the specifics of the interconnect to which they attach In the case of the interconnect to which the processor interfaces a dependent relation exists in terms of defining the particulars of logically invisible properties These consist of electrical signaling and timing considerations Although all devices attaching to the same interconnect as the processor have to observe compliance with the particulars of its specification their dependence relation extends no further In earlier systems utilising Unibus Var
187. ests are not required to provide their own linkage between discovery of sought after devices and configuring their own code to access them 6 2 4 Type System Evolution The impact of a type system evolving more slowly is that not just new or additional devices but future devices can be brought into a home and have an increased likelihood of being used For distributed systems this means a greater capacity to endure Users have the possibility of being able to utilise future devices brought into the home Developers formulating requests for existing devices gain by coverage extending to those not yet produced Specifying enabling technologies principally interconnects involves less work since device descriptions are independently defined Device manufacturers need to prepare device descriptions and integrate driver code within 6 2 5 Describe Devices to be Granted Access Gaining access to devices by describing them impacts new devices being brought into the home context Requests are more likely to extract some functionality from them where previously all or nothing was possible By ensuring access configuration becomes less brittle distributed systems are made more flexible Users as stakeholders find new devices are more likely to be gainfully employed for a given task even if only minimally Developers framing requests need to put considerable thought into structuring descriptions to ensure they capture the greatest extent of functionali
188. et CompRQ RQ RQGroup Device DGroup _ SubMatch Match getRequesterSpec Requester Spec applyRQSubMatch Mode Requester Spec Outlet CompRQ RQ RQGroup Device DGroup SubMatch applyRQSubMatch Mode Requester Spec Out Let CompRQ RQ RQGroup Device DGroup H T M_C_SCTerm RQMC RQSA RQOCI DMC DSA DCI DRU SubMatch H app lyCodeInter face Mode Requester Out Let CompRQ RQ RQGroup Device DGroup RQOCI DCI applyCodeInterface _ _ _ _ _ _ _ _ Ll end of list applyCodeInterface _ _ _ _ _ _ _ _ l _ no correspondence only DCI applyCodeInterface _ _ _ _ _ _ _ _ _ no correspondence only OCI app lyCodeInterface Mode Requester Out Let CompRQ RQ RQGroup Device DGroup OCIH OCIT DCIH DCIT device _ Device DSpec _ codeInterface DSpec DCIH DCInterface registerCodeInterface Mode Requester Out let CompRQ RQ RQGroup OCIH Device DGroup DCIH DCInterface applyCodeInterface Mode Requester Outlet CompRQ RQ RQGroup Device DGroup OCIT DCIT insert or delete code interface into or from database registerCodeInterface apply Requester Outlet CompRQ RQ RQG OCIH Device DG DCIH DCInterface assert codeInterfaceTable Requester Out let CompRQ RQ RQG OCIH Device DG DCIH DCInterface registerCodeInterface remove Requester Outlet CompRQ RQ RQG OCIH Device DG DCIH DCInterface retract codeInterfaceTable Requester Outlet CompRQ RQ RQG OCIH Device DG
189. et block stream send_receive test_set data block bytes data width bits data rate Hz figure 4 9 category subcategory decomposition into aspects aspect values Modules become elements Presently our framework comprises a suite of categories describing form and function in a hierarchical structure that decomposes into sub categories aspects and aspect values An observation concerning the categories derived is that they are not unrelated There are categories that are more correctly expressed as attributes of others in the case of user interface or task element they both requiring system resources e g interrupt expressed using the category logical requirements Similarly physical manifestation describes not only user interfaces but also electrical interfaces by specifying exterior connectors Arising out of this analysis is the need for a further expansion above categories using what we will refer to as a module There are four which satisfy the condition of being related and emerge as modules namely e task elements e user interface e communications link e electrical interface Importantly modules emerge as capable of representing what we have referred to earlier as device elements at a finer granularity than a whole Their description decomposes into the categories we have presented Consequently it is modules that are related with respect to data flow and the links between them captured by the category logical structure T
190. etwork node s name it sends requests to a reserved multicast address As the network scales Zeroconf addresses service discovery requirements across a wide area with a centralised repository for information DNS server This is combined with protocols for registering device services plus updates and queries DNS protocol and security mechanisms Zeroconf represents a refinement of an existing aspect to P networks where service discovery DNS SD is accomplished by performing a lookup on DNS pointer records using a service identifier within a domain Responses list uniquely named instances of that service across the local domain These names can be browsed to select an appropriate candidate Web services represent a range of specifications for a framework to support software components exporting functionality that can be discovered and accessed over a network especially the Internet Devices provide services which are defined by Devices Profile for Web Services DPWS which builds on Web Services Description Language WSDL Weerawarana Chinnici et al 2002 Microsoft Corporation 2006 DPWS pulls together a core subset of the specifications to define a minimal set of constraints for implementing secure Web services Discovery is described by the Web Services Dynamic Discovery WS Discovery protocol Microsoft 2005 In simple ad hoc deployments involving a minimum of network services devices and clients respond directly to annou
191. f a description Control points on the other hand send messages searching for devices and or service types Matching is conducted on interested control points for new devices and on all devices for a request The algorithm in both cases involves matching a simple text string against the search criteria A control point matches when the available device or service type is the same as it is requesting On a device the requested target matches if the device or service type is supported by itself By returning a response back to the original sender of the message a device is said to be found on a network If a control point has received a response or has matched to one newly available it learns more by retrieving a device s description This is accomplished by using the return address and location provided by the device in the discovery or response message The content is expressed in a particular format including manufacturer specific information along with a list of services offered A contrasting example is the split process used in a Jini system A lookup service acts as a broker dividing composition into two aspects as detailed in figure 2 15 Discover defines the way a device service becomes part of a Jini grouping federation and ookup reflects the current members and acts as a way of finding services Jini Device lookup service _ ____ client registrar registrar 4 t se
192. forts consist of physical co deployment of driver code on persistent storage as an approach taken by device manufacturers when releasing a product Other efforts have enlarged the universe of drivers e g system updates for commercial 24 operating systems Progress has been made in enhancing the portability of code for execution across multiple processors e g Taos OS amp LLVM Edge Magazine 1994 Lattner and Adve 2010 Also some work towards driver code executing on multiple kernels e g Linux drivers used with L4 Helmuth 2003 A comprehensive approach is required One that targets all the non fundamental and non inherent aspects to dependencies Without their alleviation or removal devices that deploy independently or are developed after a system platform is defined will not be able to connect to computer systems and unconditionally be made operational The flow on effect for distributed systems is reduced flexibility and a brittleness to system configuration 25 2 4 Composition Significance to a distributed system The intent behind a composition stage is to establish access to devices by satisfying requests This process is predicated on having decided how devices are to be described and requests framed Composition is the means by which access is granted to remote devices Discovered and configured devices plus requesters are who participates in a process conducted across a distributed system How satisfaction happens d
193. fy matchTransaction requester outlet1 composite_rqi rql rqgroup1 imic2 dgroup2 28 electrical_interface 1 01 11 task_element 1 11 task 1 1 1 1 1 0 function 1 1 1 1 bit_resolution system bit 16 The header first list item comprises fields related to the participants Ist 6th requester amp external communications identifier outlet1 plus alternative composite_rq1 request rq1 amp RQGroup rqgroup 7th 8th device amp DGroup dgroup2 9th acceptance measure amp summation of certainties 28 10th actual structural description of the correspondence described Within a structural description a series of annotations empty square brackets are included alongside branch and leaf terms They are transferred directly from the device and requester structural descriptions as correspondence is found Refer to the section on process enhancements for further details 5 1 3 Dealing With Uncertainty We are exploring structural matching and not matching of named types The upshot of this approach is that the problem domain is not categorical That is results are not expressed as finding a match or nothing at all rather they represent partial correspondence From the outset we assume that a match will exhibit less than direct correspondence because requests are expressed using structural descriptions This cr
194. g queueing asymmetric interrupt symmetric interrupt Additional Categories under synchronisation by interrupt interrupt handler location unsolicited inputs vs locking input units until a read issued I O to cache vs I O to memory I O controllers with virtual address mapping vs requiring pre mapped physical addresses figure 4 7 Smotherman s sequencing based i o taxonomy 85 Operating systems research concerned with driver code development has broken down aspects of control in a way that is applicable to device elements The Termite project utilises a device specification in an effort to improve driver quality through automatic synthesis Ryzhyk Chubb et al 2009 Device based interfaces accessible to driver code are expressed in a language that is operating system independent Interaction between driver code and device is expressed as messages which can carry data as arguments The language also models software s view of device behaviour This is modeled as a state machine whose transitions are triggered by messages Similarly Devil an Interface Definition Language is used to specify the functional interface of a device from which to generate driver code stubs to operate a device Reveillere Consel et al 2000 Reveillere and Muller 2001 They articulate points of logical control in terms of device variables which are defined by registers and are in turn defined by ports representing physical addresses Implemented f
195. g low_pass_filter analog antialiasing filter analog dynamic_range dB analog signal to noise_ratio dB analog total _harmonic_distortion digital high pass_filter digital linear_causal_filter digital_decimation_filter ddf_stop_band_attenuation dB ddf_pass_band_ripple dB Device Comparison M Audio Griffin iMic v2 Audiophile USB Tascam US 224 TE DAC TE DAC TE DAC digital to_analog digital to analog digital to analog 32 44 1 48 32 44 1 48 96 44 1 48 2 1 2 1 2 8 16 16 24 16 24 true true false 93 107 96 109 97 0 005 0 002512 0 007 false false false false false false 43 75 0 1 0 1 0 005 0 005 true true M Audio Griffin iMic v2 Audiophile USB Tascam US 224 TE ADC TE ADC TE ADC analog to digital 8 11 025 22 0532 44 1 48 2 8 16 false false true 89 89 0 01 true true true 65 0 05 0 05 oversampling digital interpolation filter true 156 analog to digital 8 11 025 22 0532 44 1 48 96 1 2 16 24 94 108 0 002512 true true 80 0 005 0 005 analog to digital 44 1 48 1 2 16 24 97 0 007 Electrical Interface Comparison illustrative sample only module electrical_interface EI category characteristics subcategory electrical aspects data_format connection_establish signal impedance ohm signal ended line_level dBu line_level dBu signal to_noise_ratio dB dynamic_range dB total_harmonic_ distortion module electr
196. ga 2010 and platform designs employing VESA Local Bus refer to comparison discussion between VESA and PCI Shanley and Anderson 1995 interconnects this applies to all devices connecting to them Recent interconnects namely HyperTransport HyperTransport 2008 used for direct processor attachment have achieved a level of specification independence such that they are no longer reliant upon consideration of the processor design 9 Driver Code Upon Platform Configuration Code The boot process for a computer system has driver and platform configuration code as distinct entities They execute during different phases of system operation one in order to boot the operating system the other once it becomes operational System resource provisioning is a dependency concern for the device itself but not its driver On the assumption that driver code will disregard the state it finds a device in and proceed to configure from scratch there is no dependency present 23 2 3 2 Impact of Dependencies The objective in preparing devices for operation is to permit dynamic construction of a distributed system without placing undue restrictions on the process Devices are however constrained by dependent relations within a computer system They require particular conditions be met to have configuration happen successfully The criticality of each dependency varies Some are fundamental to the organisation of a device attached to a computer system whilst
197. gle number in the 2nd square brackets with greater emphasis placed upon matching the conversion direction and role as converter At the branch level there are additional weightings of zero value left hand number in 4th set of square brackets However there are comparisons requested with the certainties summation right hand number To illustrate the idea of building a sub match the lower function subcategory comparison is obviously a lesser threshold than the higher task_element module level Failure of either results in the sub match being rejected which causes a flow on effect of failing to reach a later threshold for acceptance 116 Ranking request alternatives At the level of alternatives the requester needs to stipulate which options are more significant Alternatives represent differing ways of expressing a request in circumstances where the ideal is not present and compromise is essential They are expected to vary in their ability to be satisfied Our approach is to offer the capacity to rank alternatives by assigning each a priority This allows the process to accept matches for alternatives that are assigned a higher priority than an existing match It also provides a means of determining when a match is deemed to have reached a requester determined threshold and requires no further improvement In presenting alternatives to pursue we utilise a simple certainty scheme A ranking is assigned in the form of a priority value to each
198. gnal_ended matched value fug us enum unbalanced A term data_format matched value uq us enum fanalog A term connection_establish matched value ua us enum hot_pluggable accept submatch match factor check 4 gt 2 M C SC term electrical M C SC term characteristics A term direction matched value _fug us enum input A term classification matched value lig us enum Etera A term direction matched value uq us enum input A term classification matched valus Tague Gnun Fexternal A term data format matched value ug us enum analog connection establish matched value ug us enum Lhot_pluggable accept Submatch maten Faeton check 3 C SC term electrical CSC term characteristics A term direction matched value A term classification matched val A term direction matched value uq us enum input A term classification matched value uq us enum external A term signal_ended ue ug us enum unbalanced A term data_format lt ug us enum analog A term connection establish matched value ug us enum Lhot_pluggable ccept submatch match factor check 4 gt C term electrical C term characteristics A term direction matched value uq us enum input A term classification matched value ug us nu Beeman A term direction matched value ug us eum inpi A term classification matched value ug us enum r external FHELELEAT ETE EE HHHH FEET EEE ET EE EE TEETH TEE
199. group2 from Device red_1 imic2_1 HEHHEHE HHHH EEP ETE EETEEEETEE TEEPE EEE EE EEE EEE TEEPE ttt et gt checking availability of Registration Unit audio_stream_out available A term direction matched value uq us enum digital_to_analog A term sampling_rate matched value frequency hertz 48000 A term data_channels matched value system integer 2 A term bit_resolution matched value system bit 16 accept submatch match factor check 9 gt 9 M C SC term function A term principal matched value uq us enum convert SC term role SC term task ccept submatch match factor check 14 gt 14 SC term task_element A term direction matched value uq us enum unidirectional A term logical_channels matched value system integer 2 A term signal_format matched value uq us enum digital A term model matched value uq us enum stream accept submatch match factor check 6 gt 4 M C SC term Link A term compression matched value uq us enum uncompressed A term data_format matched value uq us enum pcm_audio accept submatch match factor check 6 gt 5 M C SC term channel M C SC term primitives accept submatch match factor check 12 gt 9 M C SC term communications_Link FHAPELEET ETE ET HHHH HHHH HHHH EEE ETE ETE TEETH ETE TEETH EEE t ttt checking have an acceptable RQGroup match comparing match factors is 26 gt 23 M C M C a M C RQGroup match found with DGroup
200. gt checking availability of Registration Unit audio_stream_in available A term direction matched value ug us enun Langlog to digitat A term sampling_rate matched value frequency hertz 48000 A term data_channels matched value system integer gt fn A term bit_resolution matched val System bit 16 accept submatch match factor check 9 gt 9 M C SC term function A term principal matched value uq us enum convert M C SC term role M C SC term task accept submatch match factor check 14 gt 14 M C SC term task element A term direction matched value uq us enum unidirectional A term Logical channels matched valde Csystem integer z 2 A term signal_format matched value uq us enum digital A term model matched value ug us enum Cstream accept submatch match factor check 6 gt 4 M C SC term link A term compression matched value pug us enum funconpressed A term data_format matched value uq us enum pcm_audio accept submatch match factor check 6 gt 5 M C SC term chanhel M C SC term primitives accept submatch match factor check 12 gt 9 M C SC term commlinications Link M Me A term principal matched value uq us enum adjust C SC term role gt checking availability of Registration Unit audio_stream_in available A term configure matched value uq us enum required M C SC term approach M C SC term control A term data_format matched
201. h is articulated in the specification refer to section 9 1 USB 87 device states Compaq Hewlett Packard et al 2000 239 A contrasting expression of state is a PC101 keyboard controller Intel 8042 on an ISA interconnect IBM PC system platform In this example a byte is read at an i o port address to access a status bit indicating whether the keyboard buffer contains codes corresponding to key presses Gilluwe 1997 Distinguishing interconnect bridges Part of accounting for device attachment involves consideration of the interconnect and its interface to the rest of the computer system A discrete element referred to as a bridge acts as an intermediary in communication between interconnects This involves functionality that distinguishes them from other devices attached to the same interconnect Being an intermediary is a property which marks bridges as distinct devices themselves An Intel Architecture IA 32 platform is representative of a bridge implementation involving the PCI interconnect MSI 2004 Integrated onto the mainboard is a bridge device that acts as an intermediary between the interconnect to which the processor is attached and the PCI interconnect proper Devices are then attached to PCI and communicate with the processor via the bridge refer to Intel 975X ICH7 PCle chipset Intel 2005 Intel 2006 Properties related to operational control The categories to be distilled from the discussion begin with the con
202. h will be found amongst one or more devices Results need to be applied back with both requester and device s to configure access and update resource availability In a distributed context application of them is likely to be on systems remote from where matching was conducted The results packaged in a suitable form for distribution are sent to the system where the device is connected Once they are applied the record of resources available on that system will reflect an allocation Results are also sent to the system where the requester is located We assume they present a request as a series of options and rank them This will be discussed in the next chapter under request formulation Consequently the process may satisfy an option of a higher ranking than an existing match This means that prior to applying the result a pre existing match must be cancelled If this happens reference is made to a stored result which is used for its removal with the requester The result is also sent to the system where the device involved in the pre existing match is connected To finish the new match is applied with the requester and access enabled according to the results Where a pre existing match was cancelled the positive change in device resources triggers the process again 3 4 6 Changes to Computer System Specifications Service embedded in a processing module and an integral part of system software Our intention is to target a context where inde
203. hardware and software designed to integrate various audio video and environmental tasks into a home automation and entertainment system Current commercial systems for home automation offer a wide range of applications refer to Smart Home products Savant Systems 2011 Control4 2013 The example chosen is an actual installation of a currently available product Electronic House 2011 The implementation uses mobile phones or tablets as touch screens to access sub systems in the house Configuration and control software executes on a computer system acting as the server There are wall mounted keypads used for simple control operations Sensors are used for detection as are cameras and spread throughout the house are display screens and speakers In more detail specialised control units mobile phones and tablets are used to connect with and control displays audiovisual components lights cameras thermostats security systems and other home automation equipment These units are distributed throughout the house The server is coupled with control units and provides a control interface by virtue of an application There is the option to display an interface on a television and have navigation performed via a handheld remote control The user interface is consistent across control units and server application They may be utilised to stream audio video content throughout and signal adjustments are possible per any custom setup e g close pool cov
204. he implications for taxonomic structure are that categories and their decomposition are orthogonal to modules This leads to the same categories appearing in differing modules All that that remains to complete the taxonomy is to capture properties attributable to the level of a whole device Whilst we intend for modules to be the level at which structural typing happens there are circumstances where expression of device properties is required at the level of a whole For example where power is being sourced from an interconnect power consumption of the device as a whole is preferable to expression on a 96 per module basis OpenHCI 2000 Texas Instruments 2003 Consequently a separate module is introduced referred to by the term general to capture properties of the device as a whole 4 3 3 A Taxonomy of I O The empirically derived framework comes together as a structured i o taxonomy appearing in figure 4 10 Interpreting the structure begins with the modules appearing across the top of each column Their categories are listed down the left hand side and the sub categories listed in the boxes themselves For reasons of clarity the breakdown into aspects has been omitted figure 4 10 i o taxonomy 97 gt Modules communications 5 electrical general task element A user interface
205. he vendor to maintain 27 SCSI bus generic 8259 ISA EISA PCI IDE VO VO x APIC mass storage floppy disk base system generic 8237 ISA EISA DMA controller IPI peripherals generic 8254 ISA EISA x2 system timer RAID generic RTC ISA controller ATA with single DMA chained DMA generic PCI hot plug controller Ethernet keyboard controller Token Ring digitizer pen FDDI input devices mouse controller network controller ATM scanner controller ISDN gameport controller generic WorldFip docking stations generic docking stations bridge device PCIl to PCI subtractive decode semi transparent PCMCIA PICMG 2 14 Multi Computing 386 486 Pentium VGA compatible Alpha z 8514 compatible processors PowerPC display controller XGA MIPS 3D Co processor video IEEE1394 Firewire OHCI multimedia device audio ACCESS bus computer telephony Serial Storage Architecture SSA RAM USB UHCI OHCI EHCI memory controller iach l Fibre Channel host bridge serial bus controllers System Management Bus SMBus ISA EISA MCA InfiniBand IPMI SMIC Keyboard Ctrlr Block Transfer Interface SERCOS interface standard NuBus CANbus CardBus iRDA compatible RACEway ANSI VITA 5 1994 consumer IR InfiniBand to PCl wireless controller RF generic XT compatible seri
206. he who by ensuring devices are made operational Once constructed a IO Composition service deals with the who and how to conduct the process that will automatically establish access to devices 45 3 2 IO Discovery Service The JO_Discovery service is tasked with managing awareness of device functionality in a distributed system It seeks to overcome the separation of composition from the flow of events in existing systems We address the shortcomings in current approaches by a comprehensive raft of changes From an expanded awareness of device connections through to recording distributed connections this service maintains a dynamic picture of a distributed system The primary aim of this service is to provide awareness to the distributed system of hardware signaling on each computer system that is of relevance to composition We accomplish collective decision making on the assignment of responsibility for devices to computer systems and where matching will occur in the distributed system 3 2 1 Tasks Performed by the IO_Discovery Service Enumerate the devices attached to a computer system The first of the tasks performed by the IO_Discovery service is to account for those devices permanently attached to a computer system Once powered on a system is assigned the responsibility for making devices operational As successive interconnects are probed notification is passed the IO_Configuration service and devices are made ready Success
207. hecking have an acceptable RQGroup match comparing match factors is gt 23 gt gt gt gt gt gt gt try another DGroup dgroup2 from Device red_1 imic2_1 FHELETEAT ETE ET HHHH HHHH EEE ETE ET EEE ETE ETE TEETH EEE t ttt gt checking availability of Registration Unit audio_stream_out available A term sampLing rate matched value frequency hertz 48000 m system integ ni A term bit resolution matched value systembitse A term principal matched value uq us enum iconvert C term role C term task A term operate matched value uq us enum required l C SC term approach CISC term control term operate matched value ua us enum Crequired A term direction matched value uq us enum unidirectional A term Logical channels matched value systen integer 21 A term signal_format matched value uq us enum faa ital el matched value ug us enum Estrea J accent Ssubnatch match factor checi M C SC term Lin A term conn ession matched value ug us enum uncompressed m data format matched value _ yq us enum pcm_audio accept wane cts pateh fator check e M C SC term channel M C SC term primitives accept submatch match factor check 12 gt 9 M C SC term conmunications_ FHEPETEAT ETE ET EEE ET HHHH ET EEE EEE ETE EE ETE E TEEPE TEEPE ttt Et checking have an acceptable RQGroup match comparing match factors is 12 gt 23 gt gt gt gt gt gt gt try
208. hese additions is explained More complex requests The base definition of a request lacks flexibility to how sought after devices are described It bundles all associated modules into a single structure used to match to a device Where requests become more complex the likelihood of strong correspondence lessens and the requester is faced with having to settle for incomplete satisfaction For example a request for audio streaming in and out functionality may be composed against devices that provide only one or the other which generates a less than satisfactory result We require greater flexibility to how requests are expressed to allow them to span devices This could be accomplished by deciding RQGroups can match to differing devices However this becomes confusing where multiple RQGroups are needed to describe each device Consider the example of an audio control surface where separate audio channels have user interface controls to adjust the incoming signal A request for multiple channels plus corresponding electrical connectors is complex Finding correspondence becomes brittle where devices have less channels than desired or differing electrical connectors Instead we chose to express a composite request as a list of requests making it possibly for more than one device to be part of the match result At the same time this separates the expression of association within a device from specifying whether multiple devices can satisfy Seeking
209. hrough the process itself Existing systems leave arbitration to the driver to sort and it is separate from composition The extent of sharing possible is also left to be determined by the driver 88 ALSA Project 2007 Our approach examines how sharing and arbitrating access is expressed at the level of device hardware Secure access At the hardware level a simply composite audio device with codecs for handling input or output of audio streams demonstrates that the allocation of elements can be separated functionality similar to Griffin iMic v2 Texas Instruments 2007 Either stream has distinct control thereby enabling input to be unrelated to output and the USB interconnect used for communication is shareable To provide an illustration of how secure access has been implemented we make reference to the Firewire interconnect and examine three levels of granularity refer to OHCI PCI to Firewire adapters Via Technologies 2001 Texas Instruments 2003 At the lowest level the chipset provides set clear registers that is bit fields are set via a separate address to that used to clear with reads being performed on either location This enables the updating of a bit through a write without a read beforehand Specifically the action is atomic and ensures no unintended side effects from others simultaneously doing the same OpenHCI 1997 11 12 Communication procedures are characterised by scatter gather memory buffers and employ a s
210. i link interface Categories rA SubCategories information description description description description description specification specification specification specification specification task domain dictionary logical connection connection connection connection structure relation logical device superset system resource device subset device subset requirements environment physical system resource system resource physical physical dimensions physical dimensions physical dimensions manifestation physical weight mechanical operation structures structure fault tolerance logical detection logical detection logical detection reporting reporting reporting guarantees guarantees guarantees control approach approach approach commands commands commands arbitration logical access logical access logical access input serialisation input serialisation input serialisation output selection output selection output selection timing power on performance performance performance clock power power sink management power states task primitives link channel interface interface physicality sensory mapping characteristics electrical 4 4 Device Typing A rich set of terms for device description are captured in our taxonomy This framework is intended to act as a foundation for structural expression of device type Our objective is to permit introspection of form and functionality without having to identify the target through the use of a name To use during devic
211. iMic2 fails to provide logical visibility to parameters important to its operation This is left to driver code to articulate the default settings and range of allowable values that are currently specified in datasheets from the manufacturer Texas Instruments 2007 Importantly leaving it driver code to have awareness of device state falls short of elevating parameters for consideration during composition A separate means of making these explicit is required Technicals State represents data parameters of relevance to and affected by composition They are quantified using the same structure as leaf terms Adjustments to state are branch level annotations of a structural description and allowed by either participant Linkage to match results via leaf level annotations is allowed for devices During the match process these annotations are added to the results after a term and sub match have been accepted Later the annotations are used to link to rules governing the effect of applying or removing results upon state Implementation specifics The implementation references state by indicating the requirement for adjustments at the branch level for both participants and at the leaf level for devices An example at the branch level is an annotation appearing with commands subcategory inside the 2nd square bracket in a structural description task_element te2 adjust_volume control 1 commands commands1
212. ical_interface EI category mechanical_ structure subcategory structures aspects cabling classification connector connector signal lines direction link Griffin iMic v2 M Audio Audiophile USB Tascam US 224 E AudioOut EJ AudioOutRCA EI AudioInPhoneSocket analog analog analog hot_pluggable hot_pluggable hot_pluggable 10000 10000 22000 680000 unbalanced unbalanced balanced unbalanced 4 20 line 7 8 8 2 guitar 93 93 0 007 M Audio Griffin iMic v2 Audiophile USB Tascam US 224 E AudioOut false external mini_stereo_socket 3 output port 157 EI AudioOutRCA false external rca_connector 2 output port EI AudioInPhoneSocket false external phone_socket headphone_socket 2 3 input port Appendix B A Worked Example B 1 1 Introduction The principal task domain for the worked example is audio codecs and associated elements involved in processing an audio stream A 4 stage demonstration of the process of composition involves two Requesters and three Devices They are e Requester 2 narrow expression with limited alternatives seeking specific capabilities e Requester 1 more detailed expression further alternatives seeking broader capabilities Device 1 Tascam US 224 e Device 2 Griffin iMic2 v2 e Device 3 M Audio Audiophile USB The stages involve initiating the following events e Stage 1 create Requester 2 then connect Device 1
213. ication defines the electrical signaling parameters required for a device to connect and logically participate in communication IEEE 1995b IEEE 2000 The interconnect defines the manner of logical access from simple data references through memory mapping to the exchange of data packets Firewire articulates device based structures in terms of a distinct address space divided into buses nodes and then device memory Access to interconnect addresses is via distinct packet based communication ranging from asynchronous through isochronous to transmit data The logical structure of data packets delivered to or from a device are illustrated in figure 2 4 IEEE 1995b srcBusID srcBusID reserved reserved spd tLabel rt tCode reserved reserved reserved spd tLabel rt tce reserved destinationID destinationOffsetHigh destinationID rCode reserved destinationOffsetLow reserved quadletData Asynchronous Transmit Read Request Quadlet Asynchronous Transmit Read Response Quadlet srcBusID srcBusID reserved reserved spd tLabel rt tCode reserved reserved reserved spd tLabel rt Code reserved destinationID destinationOffsetHigh destinationID rCode reserved destinationOffsetLow reserved dataLength reserved dataLength reserved data Asynchronous Transmit Read Request Block As
214. ice The JO Composition service is tasked with coordination of the match process in a distributed system and linked to the IO Discovery and IO Configuration services A separation of responsibilities between services ensures a distributed system is already constructed when the process of composition begins The IO Composition service automates establishing access for requesters to devices The core objective of this service is to accomplish satisfaction of requests from a pool of devices The process is intended to be flexible in dynamically handling who participates and responsive in being conducted when resources become available 3 4 1 Tasks Performed by the IO_Composition Service Manage distributed composition The principal task performed by the IO_Composition service is to conduct matching across a distributed system Requesters and devices participate in a process on a computer system that may be remote to either or both of them Managing this in a distributed system is divided into a preparatory and wrap up stage The preamble involves responding to a positive change in device resources by triggering the process Determining who will participate begins by all systems checking for and submitting unsatisfied requests Where at least one is received further submission is sought of all devices with resources available A queued request is selected and a solution sought from amongst the device pool which satisfies the constraints As the p
215. ice _ Device DSpec _ atom_concat DSpec _ X atom_concat X DGroup StartTerm In the context of the match rule the first argument O dTerm is bound to a start term as we create the clause and bind it to a variable using the univ or predicate NewMatchTerm RQTermName OldTerm NewTerm For example if the request term is a commands subcategory from a control category and task_element module and the device has a name imic2 with dgroup2 being checked then NewMatchTerm binds to commands imic2_dgroup2_te1_control X As the search deepens by trying the match rule itself as a goal NewZerm is used as an argument and becomes OldTerm from the perspective of goal construction at the lower level c the second argument is a string concatenation of the next lower level term being sought If it can be bound then it will be a concatenation of a lower level term plus the start term and the taxonomic terms from the path taken all the way to the highest level Using the NewMatchTerm example above where X is able to be instantiated it becomes commands imic2_dgroup2_tel_control imic2_dgroup2_te1_control_commands Once a clause has been created it is used slightly differently but still reliant upon being able to bind variables At the branch level seeking all possible lower levels forces binding NewMatchTerm RQTermName OldTerm NewTerm findall NewTerm NewMatchTerm TermList member NewTerm TermList
216. icient information to establish the defined equivalence for each constructed type An equivalence function which compares two instances of such representations must also be defined Connor 1990 72 This suggests that equivalence can only be established by reference to the hierarchy of the taxonomy and use this to traverse the structural types of both devices Because a device description is the type then each DGroup in its associated list must be checked For DGroups from each device to be isomorphic their structural descriptions must be of identical construction Structural typing is static hence checking can be performed when a device description is created during code development However checking type equivalence between devices is not a pressing requirement A clearer idea of what equivalence entails really provide us with guidance on what constitutes a request That is to be able to evaluate the extent of correspondence between a request and device requests will need to be expressed in the same was as DGroups and use the same type dictionary 104 4 5 Request Formulation Adopting a structural approach to device typing does not require a request to be a description of a whole device Rather it is can be expressed as sought after elements that are significant to the requester including those relevant to control of the device Importantly a request can only be checked for correspondence against a device if we are comparing the same
217. ides input output to or from the physical environment It implements distinct functionality that is logically accessible To provide a context for discussing devices and requests for them a description is needed of the steps involved in establishing access to devices across a distributed system We introduce a model of this process and use the stages to structure our treatment of current approaches to distributed systems The key stages are drawn from those required on a computer system and are the result of devices needing to be externally controlled In broad terms the stages consist of e Discovery involves disseminating awareness of device functionality in a distributed system Configuration involves the preparation of a device for operation and participation in Composition Typically this will involve consulting a device based indication of requirements provisioning the system resources required and initialising suitable software to perform tailored configuration of the device Composition defined as a process itself for satisfying a request that is seeking access to device functionality Satisfaction involves matching a request to a pool of device descriptions in accordance with a set of guidelines In the context above device description is defined as a device based structure that indicates the sort of functionality implemented It is used by our work to contain structures defined in subsequent chapters The complement to devic
218. ientations over time e g mouse tablet light pen touch panel or screen joystick trackball keyboard eye tracker wheel glove gesture suit quantify specifying a value to quantify a measure e g switches keyboard mouse wheel microphone text capture entering text directly e g keyboard mouse 78 image capture entering an image directly e g video scanner B output device taxonomy static output providing an image on a permanent directly readable medium e g printers plotters dynamic output providing variable information on a non permanent medium e g screen head mounted display loudspeakers light figure 4 3 ECMA User Interface Taxonomy A description of the device examples is provided expressed in terms of the significant properties characterising them Unfortunately lacking an organising principle this reduces the utility to their description Of note is the exclusion of compound devices that is those having a combination of input and or output functionality ECMA consider these as lacking distinctiveness and choose to avoid adding further categories Instead they view them as combinations of input and or output functionality already described by the taxonomy The taxonomy fails to extend our understanding since the use of devices as examples only serves to reinforce properties being associated with a whole Rather than describing elements of each device they see them as parts of an interface in the interac
219. in a structural description Failure at all levels forces the match to be returned as null 136 Main steps involved The goal iterates through a list of modules in a structural description that is associated with the RQGroup It performs a systematic traversal recording correspondence between terms before returning a result For the DGroup and RQGroup being examined the steps involved are 1 construct a start term using both DGroup amp RQGroup 2 the sub goal is tried using the start term amp list of modules from the RQGroup 3 where annotated the result returned is checked for reaching acceptance measure 4 failure forces the search process to drop back to a higher goal amp try another DGroup During traversal of the list of modules a series of further steps are observed depending upon whether the search is determined to be at the branch or leaf level e fora branch term B1 term name is used to create a device term to check for its existence B2 device resource availability is verified where annotated failure on either results in a null sub match B3 recursively try the same goal using the sub structure beneath the branch term B4 check for sub match acceptance where annotated B5 evaluate match conditions where annotated failure on any of these results in a null sub match B6 calculate sub match acceptance measure B7 add branch term sub match plus annotations to results before selecting next term at the sam
220. ind a solution which satisfies the constraints from amongst the pool of devices The event sequence outlined in figure 3 13 covers the wrap up Composition continues when the outcome is that a match was found amongst one or more devices system where newly matched device is connected local remote apply_match_with_device composition apply_match with_device apply_match_with_requester system where requester is located system where pre existing matched device is connected local remote local remote from_requester 2T apply_match_with_requeste cancel_match_ l from_requester perform match S figure 3 13 perform match wrap up notes solid lines indicate sequences which occur whereas broken lines may happen depending on circumstances shaded amp boxed area indicate separate systems 70 Results need to be applied back with both requester and device s to configure access and update resource availability Firstly IO Composition distributes the results to the system s where newly matched device s are connected The IO Results support service on these systems handles applying the match by advising IO_Resources to adjust the record of resource allocation IO_Composition sends the result to the system where the requester is located IO_Results handles applying the match by notifying IO Outlets to record details including configuring access
221. ineberg 1995 Miller acknowledges overlap between task functions which he reasoned was acceptable in order to capture the continuity from input through the processes in between to response actions Some degree of redundancy is tolerated to ensure descriptive power over the transactions involved in human or machine task performance Indicating resource requirements As part of the process of preparing a device for operation software responsible for configuration requires an indication of the system resources required Providing logical visibility to these requirements is not standardised nor is reference to which resources Rather they are usually particular to an interconnect and accessible via means defined in those specifications e g access to PCI interconnect defined configuration space PCI SIG 2003 Resources variously consist of reserving main memory for device registers or i o ports or assigning a system interrupt They extend to describing system relationships in terms of capacity to initiate communication roles of master or slave and even to domain specifics of where a video frame buffer must be mapped into system memory Matrox Graphics 1999 Additional qualities concern dynamic attachment and involve more than just consideration of electrical connectivity A device must allow for and the interconnect must assign some indication of locality refer to USB amp Firewire IEEE 1995a Compaq Hewlett Packard et al 2000 Th
222. ing Requests Assertions associated with requests and devices are loaded into the database as required by connection events and retracted as a result of disconnections The adjustment happens dynamically to reflect which requests are at hand and manage the pool of devices The match process begins once systems are connected to each other Composition is conducted abstractly across the entire distributed system as a singular process 161 B 1 4 The Match Process Stage 1 Create Requester 2 amp Connect Ist Device Tascam US 224 The example begins with the First Device a Tascam US 224 having connected to a computer system and Requester 2 having arrived on another system These systems were connected together which initiated the match process The transcript begins with the match process checking for queued outlets submitted by the requester Having found an outlet this triggers all systems to check for any devices with resources available for assigning to a request Having found at least one device matching proper commences reading submitted outlet from match buffer Outlet outlet1 from Requester white_4 requester2_1 Devices with resources available Lgreen_2 us224_1 gt MATCH PROCESS BEGINS Stage 1 Match Expectations e record of matching of a RQGroup to successive DGroups e threshold match is achieved for highest priority request alternative Composite Request e record of application of match to both Requester amp
223. ing for permanently attached devices involves a different approach than a dynamic connection since there is an absence of signaling As such we deal with devices as a system is powered on through successive probing of interconnects The process artificially treats devices as connecting and automatically assigns responsibility to that system Bootstrapping of a typical system organisation as depicted in figure 3 2 begins by referencing a persistent record to determine whether any devices are attached directly to the processor s own local interconnect processing module processor local interconnect interconnect bridge primary interconnect interconnect bridge secondary interconnect figure 3 2 typical physical organisation of a system A first device is selected assigned to that computer system and notification passed to the IO_Configuration service to prepare it for operation When an interconnect bridge is encountered it is also configured for operation for further details refer to the discussion of driver code dependencies under the IO Configuration service Thereafter the bridge driver is utilised to proceed with a probe of the secondary interconnect This is where the protocol becomes a tree traversal with successive notifications sent to configure each of these devices and continue probing successive interconnects as further bridges are 49 encountered The process proceeds until there are no devices
224. ings Request rq5 Request Group rqgroup4 sampling_rate frequency hertz 48000 179 retracting existing match transaction done with cancelling pre existing match completing apply of new match removing shadowed state to complete apply with Device blue_3 audiophile_1 applying group match with Requester apply match with Requester black_5 requester_1 MODE apply code adjust_dac_settings Request rql Request Group rqgroup2 gt DeviceCodeInterface dac_configure set_sample_rate set_resolution set_channels data audio_out_settings Request rql Request Group rqgroup2 bit_resolution system bit 16 data audio_out_settings Request rql Request Group rqgroup2 data_channels system integer 2 data audio_out_settings Request rql Request Group rqgroup2 sampling_rate frequency hertz 48000 asserting new match transaction removing shadowed state to complete apply with Device blue_3 audiophile_1 applying group match with Requester apply match with Requester black_5 requester_1 MODE apply code adjust_adc_mute Request rql Request Group rqgroup1 gt DeviceCodeInterface adjust_mute_analog_in set_analog_audio_in_mute data audio_in_settings Request rql Request Group rqgroup1 signal_mute system boolean true code adjust_adc_settings Request rql Request Group rqgroup1 gt DeviceCodeInterface adc_configure set_sample_rate set_resolution set_channels data audio_in_
225. ion a logical space is defined that devices are required to implement It is referenced during configuration to determine the type of device attached PCI SIG 2002 PCI SIG 2003 The device resident structures accessible when probing PCI configuration space are detailed in figure 2 8 Access consists of reading then decoding vendor and product codes denoted by circled A followed by PCI class codes denoted by circled B byte read amp decode as default value 3 2 1 0 offset VIA Technologies Inc gt 30441106h Device ID Vendor ID 00h VT6306 Firewire 1394a controller Q2800000h Status Command 04h read amp decode as serial bus controller Firewire 1394 OHCI nn 0C0010nnh BaseClassCode Sub Class Code Prog Interface Revision ID 08h 0Ch FFh figure 2 8 PCI configuration space header for Firewire bridge device Via Technologies 2001 Together class and sub class define the type of a device These codes are arranged hierarchically as shown in figure 2 9 PCI SIG 2002 267 75 Similar functionality is grouped together and assigned a name Class codes guide enumeration during bootstrapping of a system however they are not intended to represent operational specifics Instead vendor and product identity plus revision number must be referenced to distinguish device implementations Although vendor codes are guaranteed to be unique product codes are left for t
226. ion is specific to an interconnect as is providing an indication with the device of what resource got allocated We stipulate that they be articulated in an independently defined device description This alleviates an important aspect of the dependency devices have upon interconnect specifications The IO Configuration service with an understanding of the structure of a device description can extract resource requirements and update details of dynamic allocation Link device description to driver code We acknowledge the dynamic nature of distributed systems and the importance of creating a highly responsive system A key requirement is utilising composition as a means of reconfiguring communication links following disconnections This means device access is established through this process Which in turn means driver code must be linked to device descriptions The IO Composition service with an understanding of a device description can attend to satisfying requests and utilise these links to configure access to a device Embed driver code with device The most fundamental device dependency is upon driver code for configuration and operational control In a context where drivers are deployed separately more is needed than improving the prospects of locating them to remove the problem The criticality of the dependency means physically bundling media containing driver code with the device is also inadequate Instead we want to guarantee their
227. ion of requests uses terms from the taxonomy Elements are described that can be controlled and are refined by specifying non functional aspects Complex requests are built by specifying how elements are associated allowing for the possibility of spanning multiple devices Structure is defined for presenting alternatives to pursue during composition Guidelines for specifying what constitutes satisfaction are defined The taxonomic terms are projected to evolve at a rate that is significantly slower than successive product releases by device manufacturers As such our approach is well equipped to retain the capacity to describe future devices 6 1 3 Definition of the Process of Composition Definition of the process of composition is contained within an inference engine styled to satisfy requests for access to device functionality An implementation is part of that definition An inference engine is outlined that is tailored to attempting satisfaction of requests A series of steps are defined for a match process conducted on a single computer system A requester and one or more devices are assumed to have been submitted The process 144 embodies a determination of what is involved in satisfying a request It also determines how an arbitrary pool of devices are to be composed The results of composition are linked to the granting of logical access The implementation provides an executable model of the process and a framework to explore reques
228. ions it is not possible to detect trivial matches The search may return a result that is minimal populated by few leaf terms and a minimal set of branch terms connecting them Consequently formulating a structural description for a request requires a measurement of what represents acceptable correspondence We allow the requester to specify acceptance values to ensure results are rejected that are deemed unimportant We extend its use throughout a structural description to permit pruning of sub matches during the search Significance to composition The process does not constrain how a structural description is to be arranged nor how acceptance values are assigned It simply conducts the search according to how a requester structures the presentation The requester provides a guide as to which terms and their sub structures are weighted as especially important The process provides a summation during the search and where specified by the requester checks whether it reaches the value for accepting the sub structure into the results During the search where annotated in the structural descriptions process enhancements affect whether to deepen the search include a sub match or are added to the results for processing later when applying the match The search seeks to systematically check every request term in a structural description The search is guided to select alternate bindings for device terms at the branch level since repeats are permitted
229. iption of Devices 4 1 Overcoming Named Type Restrictions 4 1 1 Assigning Types to Whole Devices 4 1 2 Assigning Types to Code Interfaces 4 1 3 Implied Device Properties 4 2 Exploring Structural Description 4 2 1 Properties to Describe Devices 4 2 2 Interaction at the User Interface 4 2 3 Physicality of Devices 4 2 4 Operational Control 4 2 5 Concurrency and Sharing Access 4 2 6 Non Functional Aspects 4 2 7 Finer Grained Description 4 3 Building an I O Taxonomy 4 3 1 Problems Encountered Compiling Taxonomies 4 3 2 Structurally Relating Terms 4 3 3 A Taxonomy of I O 4 4 Device Typing 4 4 1 Structural Typing in a Distributed System 4 4 2 Describing a Device 4 4 3 Determining Equivalence 4 5 Request Formulation 4 5 1 What Makes Sense to Request 4 5 2 Adding Dimensions to Requests 4 5 3 Seeking Access and Needing to be Controlled 4 5 4 Determining Satisfaction Composition 5 1 The Match Process 5 1 1 Systematically Satisfying A Request 5 1 2 Generating the Results 5 1 3 Dealing With Uncertainty 5 2 Process Enhancements 5 2 1 Arbitrating Access 5 2 2 Code Interfaces 5 2 3 Match Parameters 5 2 4 Quantitative Correspondence 5 2 5 Managing State 5 2 6 Match Conditions 5 3 Guiding the Search 5 3 1 Satisfying a Requester s External Access Point 5 3 2 Satisfying a Request Alternative 5 3 3 Satisfying a Request 5 3 4 Satisfying a RQGroup 5 4 Search Optimisation 5 4 1 By Structuring Requests and Devices 5 4 2 Match Process Optimisation 5
230. irections in virtual environments report of an NSF Invitational Workshop March 23 24 1992 University of North Carolina at Chapel Hill Newsletter ACM SIGGRAPH Computer Graphics vol 26 3 DOI 10 1145 142413 142416 pp 153 177 Fusion i0 2008 iO Drive2 specifications overview Fusion iO viewed February 2014 lt http www fusionio com products iodrive2 gt Garfinkel T Rosenblum M amp Boneh D 2003 Flexible OS Support and Applications for Trusted Computing In Proceedings of the 9th Conference on Hot Topics in Operating Systems HotOS 03 pp 145 150 Geihs K 2001 Middleware Challenges Ahead IEEE Computer vol 34 6 DOI 10 1109 2 928618 pp 24 31 186 Gilluwe F 1997 The Undocumented PC A Programmer s Guide to I O CPUs and Fixed Memory Areas 2nd ed Addison Wesley Reading MA USA ISBN 0 201 47950 8 Griffin Technology 2010 iMic USB Audio Interface Product Overview Griffin_ Technology viewed March 2014 lt http store griffintechnology com catalog product view id 623 s imic category 62 gt Hachman M 2011 Intel Thunderbolt Rollout Won t Be Lightning Fast PCMag Com viewed March 2014 lt http www pcmag com article2 0 2817 2380890 00 asp gt Helmuth C 2003 Linux Device Driver Environment Manual v0 5 2 4 27 Technische Universitaet Dresden viewed March 2014 lt http os inf tu dresden de l4env doc html dde_linux index html gt Hewlett Packard Inc Intel Mic
231. irtual Machines for Distributed and Networked Applications technical report 02 02 01 University of Washington Seattle WA USA Williams D Reynolds P Wlalsh K Sirer E G amp Schneider F B 2008 Device Driver Safety Through a Reference Validation Mechanism In Proceedings of the 8th USENIX Symposium on Operating Systems Design and Implementation OSDI 08 San Diego CA USA pp 241 254 Zakaria N A Kimura M Matsumoto N amp Yoshida N 2009 Stepwise Refinement in Executable UML for Embedded System Design A Preliminary Study World Academy of Science Engineering and Technology vol 31 July pp 151 153 194
232. is leads us to the middle ground in adopting a minimal specification of services to handle device discovery configuration and composition 3 1 2 Service Architecture for Composition The distributed services required relate to us targeting the separation of composition from the flow of events in current systems This isolation is overcome by providing distributed awareness of devices connecting to a computer system and linking the process of device discovery to their configuration and participation in composition Each computer system is required to run a suite of services styled for discovery configuration and composition of devices Collectively they attend to the i o related needs of a distributed system These services handle current requirements account for the trends being experienced by distributed systems and have a capacity to endure The objective is to conduct composition in a more flexible and responsive manner This means addressing each of facets to the technical challenges from the previous chapter of facilitating access to devices across a distributed system e where matching can be conducted in any distributed context encountered maintain a record of others in proximity on each computer system a determination can be made as to which system will conduct matching e who participants can be determined dynamically as the process is invoked requesters have requests requiring satisfaction a pool of devices has resour
233. isfy a request Sectioning by paying attention to form is really about spatial co location of exterior elements They may consist of user interfaces and or electrical interfaces An example is that of an audio control surface providing multiple audio channels that are selected to be mixed into an output stream Each channel consists of the same user interface elements which are used to change the channel s signal characteristics Without some way of associating interface elements into separate channels a request for elements of a channel can be satisfied in a myriad of ways across multiple channels To finalise the definition of a DGroup we transfer structural descriptions to them and specify module associations in each structural description A device description consist of a list of DGroups as follows deviceStructure imic2 dgroup1 dgroup2 dgroup3 deviceGroup imic2 dgroup1 deviceGroup imic2 dgroup2 deviceGroup imic2 dgroup3 Using this approach to association we must make allowances for DGroups overlapping where they have modules in common Typically this is the case where multiple signal paths converge on task element modules responsible for directing access to an interconnect An example is a device having both audio in and out pathways sharing the task element responsible for access to the USB interconnect We continue with the example of a simple audio codec device similar to the Griffin iMic2
234. ists of alternatives it is possible for the search to return a result that is minimal This could be by as little as a single RQGroup match where many comprise a request and there is more than one request to be fulfilled Specifying what to do when a requested ideal is not present and only minimal matches are possible was necessary to improve the quality of satisfaction Significance to composition The process attempts to find correspondence without any pre conceptions regarding the suitability of the devices present Where an alternative is insufficient compared to an existing match or one could not be found the search is guided to try further alternatives Main steps involved 1 arequest alternative CompositeRQ is selected from those associated with a Requester s external access point Outlet The use of the member operator provides a range of options to try 2 the selected alternative is checked for being preferred over any pre existing match with the failure to exceed its priority forcing backtracking to select another alternative to step 1 3 the sub goal find a request alternative match is tried using a list of requests associated with that alternative 4 any match returned must be non null a failed check results in backtracking to select another alternative to step 1 5 where successful the match is applied by altering the assertions relevant to the Requester 130 Notes a match is applied with the device as p
235. ive interconnects are probed as bridges are encountered until there are no further devices remaining to be configured A sphere of devices is built through traversal of connection paths out from a processing core Determine which computer system is to be assigned responsibility for a device Another of the tasks performed by this service is to ensure new devices are assigned to a computer system This continues on from accounting for those permanently attached to the handling of device connections We assume a signal is raised when devices connect to an interconnect which is part of a system This requires interpreting such as a notification Where a new device is encountered a computer system is assigned responsibility for its configuration Determine the computer system where composition is to be conducted A further task performed by this service is to manage connections to other systems This continues on from the handling of device connections in circumstances where a computer system is interpreted as arriving or leaving not just a device Part of managing a record of which systems form a cluster is to determine the system where composition will be conducted 3 2 2 Implementing the O_Discovery Service We are concerned with facilitating distributed access to devices within a context of systems being constructed out of independently deployed components and defined by platform specifications The nature of our contribution necessitates ch
236. k W Smith D C Irby C H Beard M amp Mackey K 1989 The Xerox Star A Retrospective IEEE Computer vol 22 9 DOI 10 1109 2 35211 pp 11 29 Kaiyan N 1993 Virtual Environments An Interactive Paradigm Honours thesis Swinburne University of Technology Melbourne Australia Kalawsky R S 1993 The Science of Virtual Reality and Virtual Environments Addison Wesley Wokingham UK ISBN 0 201 63171 7 Kay A 1990 User Interface A Personal View In B Laurel ed The Art of Human Computer Interface Design Addison Wesley pp 191 207 ISBN 0 201 51797 3 188 Kindberg T amp Barton J 2001 A Web Based Nomadic Computing System Computer Networks The International Journal of Computer and Telecommunications Networking vol 35 4 DOI 10 1016 S1389 1286 00 00181 X pp 443 456 Kindberg T amp Fox A 2002 System Software for Ubiquitous Computing IEEE Pervasive Computing vol 1 1 DOI 10 1109 MPRV 2002 993 146 pp 70 81 Lamport L Shostak R amp Pease M 1982 The Byzantine Generals Problem ACM Transactions on Programming Languages and Systems vol 4 3 DOI 10 1145 357172 357176 pp 382 401 Lattner C amp Adve V 2010 LLVM Assembly Language Reference Manual viewed March 2014 lt http Ilvm org docs LangRef html gt Leffler S J McKusick M K Karels M J amp Quarterman J S 1989 The Design and Implementation of the 4 3BSD UNIX Operating System Addison We
237. known service types is defined independently to the Jini specification The iRoom middleware is a prototype implementation of a service framework for interactive spaces It provides infrastructure support for user interface selection adaptation generation Johanson Fox et al 2002 Devices e g light projector or a scanner or applications e g web browser or presentation software implement services It is services that are intended to be controlled directly through a dynamically generated user interface Bonjour as Apple s implementation of Zeroconf is a protocol for locating device services on a local network Apple 2005 Cheshire and Steinberg 2005 Zeroconf expresses types in terms of services not hardware A service is viewed as a more comprehensive way of describing device functionality Service types are granted upon request with a registry being maintained through an industry body DNS SD org The arrangement of them can be thought of as a fleet of protocols where the original is referred to as the flagship and forms a historical record The use of sub typing hierarchically structures the namespace and serves to limit searches The SpeakEasy approach from XeroxPARC targets interoperability among a group of devices applications and services Edwards Newman et al 2002 It is predicated on an agreement to use a fixed set of interfaces that are multi purposed for ad hoc interoperability Some degree of prior knowledge is
238. l driver modules Some devices require a driver specifically tailored to them Others are intended to be managed by driver support for all devices from a particular class Once selected a driver registers the device as a member of a device interface class denoting a logical grouping of operations it supports This is done according to a globally unique identifier code assigned by Microsoft for each device interface class with vendors able to define their own unique classes where required This is organised as a collection of i o related types as detailed in figure 2 13 Battery Devices Biometric Device Bluetooth Devices CD ROM Drives Disk Drives Display Adapters Floppy Disk Controllers Floppy Disk Drives Hard Disk Controllers Human Interface Devices IEEE1284 4 Devices IEEE1284 4 Print Functions IEEE1394 Devices 61883 IEEE1394 Devices AVC IEEE1394 Devices SBP2 IEEE1394 Host Bus Controller Imaging Device IrDA Devices Keyboard Media Changers Memory Technology Modem Monitor Mouse Multifunction Devices Multimedia Multiport Serial Adapters Network Adapter Network Client Network Service Network Transport PCI SSL Accelerator PCMCIA Adapters Ports COM amp LPT ports Printers Printers Bus specific class Processors SCSI amp RAID Controllers Smart Card Readers Storage Volumes System Devices Tape Drives USB battery devices amp UPS devices all biometric based personal identification devices
239. l structure such that elements are associated in more complex ways than just belonging to that device Importantly providing an indication of how external connections relate to the rest of the device Connected elements may not necessarily account for all that comprises a device nor may they correspond to the organisation of the device s circuit layout Capturing the connections forms an integral aspect of constructing a device description where the elements are not a flat hierarchy Rather where there is a structure to the connections which is open to being logically introspected Data communication between elements Structuring a device out of elements means stitching them together to form a single entity These elements comprising external connectors implemented functionality and user interface components are connected together The links themselves can be described as having a structure to the data or signals being communicated They concern descriptions of internal and external connections to from the device Characterising the link between elements also concerns each of the channels At this level sequencing communication data formats or the qualities of an analog signal are relevant properties An initial example of a communication link is data transmission using packets across the Firewire interconnect IEEE 1995b IEEE 2000 Communication is framed as transactions by send multiple packets back and forth A series of operations un
240. le Devices Overview of the restriction The most prevalent assignment of types is at the granularity of a whole device This practice is widespread happening at all levels of software responsible for device configuration and extending to abstractions used to represent hardware Identifying the type of a device attached to a computer system is reliant upon interconnect specifications through to platform configuration code refer to PCI interconnect amp EFI platform PCI SIG 2003 Unified EFI Forum 2009 With names assigned denoting discrete devices the only possible means of discerning what is connected is at the level of a whole This rigidity persists with the abstractions used for driver code development environments The types available refer to whole devices and identification of functionality at any other granularity is not accommodated refer to Apple IOKit framework Apple 2007 In a distributed context middleware has adopted a coarser granularity where multiple devices are denoted by use of a name refer to ubiquitous computing Kindberg and Fox 2002 Making reference to artifacts comprising multiple devices moves even further away from getting at the functionality comprising each device How to overcome these restrictions To be in a position where functionality can be articulated we need to avoid a course grained approach to setting types This requires identifying devices by finer means than reference to a whole We propos
241. liable nature of data communication devices send a set of discovery messages multiple times with a delay in between When a control point discovers a new device it must use the resource location URL in the discovery message to retrieve a description expressed in XML syntax and based on a standard UPnP Device Template Alternatively when a new control point is added to the network SSDP allows it to discover devices that are connected to the network Thus by listening to the standard network address control points and devices can be made aware of new services being offered and respond to service requests In each case the response is a discovery message that contains specifics about a device and its services Any interested control point can listen for device available notifications whereas all devices must listen for search requests During discovery IP multicast is used for real time communication to associate a sender with a group of interested receivers This is accomplished by using specially reserved addresses in IP networks where the source is not required to know about receivers in the group However state information must be stored on intermediate network routers consisting of routing and forwarding entries for those interested An entry is recorded for each tree where a router has downstream receivers with tree construction initiated by receivers When a sender uses multicast addressing for a message intermediary routers must mak
242. lightning digital av adapter surprise gt PCI SIG 2002 PCI Local Bus Specification revision 2 3 standard PCI SIG Portland OR USA PCI SIG 2003 PCI Express Base Specification revision 1 0a standard PCI SIG Portland OR USA Pering T Want R Rosario B Sud S amp Lyons K 2009 Enabling Pervasive Collaboration with Platform Composition In Proceedings of the 7th International Conference on Pervasive Computing Pervasive 09 DOI 10 1007 978 3 642 01516 8 14 pp 184 201 Pierce T 2004 Implementing EFI On 32 Bit Systems Windows Hardware Engineering Conference WinHEC Seattle WA USA 190 Pike R amp Thompson K 1993 Hello World In Proceedings of the Winter USENIX Conference USENIX 93 San Diego CA USA Ponnekanti S R Lee B Fox A Hanrahan P amp Winograd T 2001 Crafter A Service Framework for Ubiquitous Computing Environments In Ubiquitous Computing Ubicomp p 19 Presotto D amp Winterbottom P 1993 The Organization of Networks in Plan 9 In Proceedings of the Winter USENIX Conference USENIX 93 San Diego CA USA p 13 Project UDI 2001 Uniform Driver Interface UDI Core Specification volume I standard v 1 01 Project UDI Project UDI 2001 Uniform Driver Interface UDI Core Specification volume II standard v 1 01 Project UDI Reveillere L Consel C Marlet R Merillon F amp Muller G 2000 The Devil Language reference man
243. ller Device I O provides basic Memory I O amp PCI interfaces used to abstract accesses to devices USB bus support USB Host Controller provides basic USB host controller management basic data transactions over USB bus amp USB root hub access USB I O provides services to manage amp communicate with USB devices I O subsystem using SCSI Pass Thru provides services allow SCSI Pass Thru commands SCSI command packets sent to SCSI devices attached to SCSI channel figure 2 11 fundamental elements of Extensible Firmware Interface EFI Platform configuration responsibility has been extended past when an operating system kernel gains control The Advanced Configuration and Power Management ACPI specification was developed to provide enhanced power management functionality It details a set of interfaces for device control that persist for use by an operating system Hewlett Packard Intel Corporation et al 2009 Unified EFI Forum 2009 These platform integrated devices are defined in the ACPI standard some using identity codes according to their functionality others not assigned an ACPI code A breakdown of these functional groupings is as follows e ACPI namespace based integrated device IDs Generic Container Device Embedded Controller Device Control Method Battery battery Fan causes cooling when on Lid Device lid status Power Button or Sleep Button Device power button functionality PCI Interrupt Link Device all
244. lly configure data variables belonging to the requester are also covered Both provide a comprehensive means of accomplishing automatic configuration of control 109 4 5 4 Determining Satisfaction As the structure of a request was progressively defined we discussed satisfaction in terms of it either happening or being inadequate Some sort of guidance is needed regarding what constitutes satisfaction alongside the definition of a request Our discussion identifies the key problem areas and explains why guidance is necessary Then each of these areas are treated separately from satisfying a request at the top level through to checking correspondence in structural descriptions Why do we need to guide composition The need to guide composition and involve the requester in determining acceptance is due to two factors request structure and derived correspondence Firstly the structure of a request permits multiple items be they alternatives requests and RQGroups The guidance required concerns how to treat them when presented with a list This extends to resolving whether any items from the list are allowed to fail to find a match The extent of correspondence that exists between structural descriptions is uncertain and necessitates guidance regarding how to determine acceptability along with an indication of what constitutes unsatisfactory These decisions rest with the requester because they define the structure used to check correspondence
245. location of control and access arbitration A demonstration of structural matching is provided through a fully worked example We set out to build a distributed system with sufficient capability to investigate structural matching between requests for functionality and device identities Furthermore to accomplish this dynamically when devices connect and permit access to their functionality as the outcome of matching requests The resultant schema presents a comprehensive solution by combining a structured language expressive enough to describe current devices and future possibilities with a tailored inference engine designed to compose an entire distributed system iii iv Acknowledgements A research program spanning more than a decade would not have managed to sculpture a significant contribution to knowledge without the collective support and contributions from key people in my life Francis in his role as principal advisor receives a debt of thanks that runs deep The project that I came to you with required an extraordinary supervisor to mould it into a shape where it could fit it into a thesis Together we dared to dream of a better world to explore computer science at the edges of what was possible and to look up at the blue sky and wonder Chris as the overseeing advisor always the sensible and wise one I am grateful to you for encouraging Francis and I to make something of this unique opportunity to work together Also for
246. log A term conn ction_establish matched value ug us enum hot_pLuggable accept submatch match factor check 4 gt 2 M C SC term electrical M C SC term characteristics term classification matched value ug us enum externa A term classification matched value uq us enum external A term data format matched value ug us enum analog A term conn ction_establish matched valu ud us enum hot_pLuggable accept submatch match factor check 3 gt 2 M C SC term electrica M C SC term characteristics A term classification matched value ug us enum externa A term classification matched value uq us enum external A term signal_ended matched value ug us enum unbalanced A term data_format matched value ug us enum tanalog A term conn ction_establish matched value ug us enum hot_pLuggable accept submatch match factor check 4 gt 2 M C SC term electrical M C SC term characteristics A term classification matched value ug us enum externa A term classification matched value uq us enum external HEHHEHE ETE HHH HHHH HHHH HHHH EEE ETE ETE TEETH EEE EEE TEEPE ttt tt checking have an acceptable RQGroup match comparing match factors is gt 23 gt gt gt gt gt gt gt try another DGroup dgroup23 from Device green_2 us224_1 HEHHEHE HHHH HHHH FEET EEE ET EET ETE ETE EE ETE ET EEE EEE EEE t ttt gt checking availability of Registration Unit analog_audio_s
247. lved as awareness is managed automatically Additional requirements do arise for developers of enabling technologies in this case interconnects to provision the ability to detect connection and disconnection events 6 2 2 Driverless Operating System A driverless operating system means new devices can be brought into the home and their functionality made available automatically For distributed systems this means that despite independent deployment devices still get configured and no longer require consideration of which operating system Users experience a more robust system and can rely upon devices being made ready for use A reduced need to manually sort device configuration issues means less system administration Operating systems developers experience dramatically less preparation time by only implementing a driver execution framework Device manufacturers also experience less duplication of effort in having to provision a single version of driver code 145 6 2 3 Matching Linked to Connection Events Linking matching to connections means a home system can dynamically configure control units as a result of devices arriving Distributed systems become more responsive ensuring not only device configuration happens but their participation in composition Users experience a context which self configures and where additional devices can be brought inside the home There are reduced system administration responsibilities Developers of requ
248. m relation M C SC term Logical_structure A term signal_ended matched value uq us enum unbalanced A term data_format matched value uq us enum analog A term connection_establish matched value uq us enum hot_pluggable accept submatch match factor check 4 gt 2 M C SC term electrical M C SC term characteristics A term width matched value length mm 8 3 M C SC term physical_dimensions M C SC term physical_manifestation A term connector matched value uq us enum rca_connector rca_connector A term direction matched value uq us enum Linput A term classification matched value uq us enum external accept submatch match factor check 8 gt 7 M C SC term structures M C SC term mechanical_structure A term device_boundary matched value system boolean true M C SC term relation M C SC term Logical_structure accept submatch match factor check 14 gt 9 M C SC term electrical_interface HEHHEHE HHHH HHHH FEET EEE ET EEE ETE ETE EE ETE EEE EEE EEE PETE Et checking have an acceptable RQGroup match comparing match factors is 54 gt 42 RQGroup match found with DGroup dgroup12 from Device blue_3 audiophile_1 adding match for RQGroup rqgroup1 to match list for Request rq1 177 apply match with Device blue_3 audiophile_1 MODE apply Request Group rqgroup1 Device Group dgroup12 registration units analog_audio_stream_in updated gt unavailable state update
249. m task_element A term direction matched value uq us enum unidirectional A term logical_channels matched value system integer 2 A term signal_format matched value uq us enum digital A term model matched value uq us enum stream accept submatch match factor check 6 gt 4 M C SC term Link A term compression matched value uq us enum uncompressed A term data_format matched value uq us enum pcm_audio accept submatch match factor check 6 gt 5 M C SC term channel M C SC term primitives accept submatch match factor check 12 gt 9 M C SC term communications_Link HEHHEHE HHHH HHHH HHHH HHHH EEE ETE ETE EE ETE ETE TEETH EE ETE tt checking have an acceptable RQGroup match comparing match factors is 26 gt 23 RQGroup match found with DGroup dgroup22 from Device green_2 us224_1 adding match for RQGroup rqgroup3 to match list for Request rq4 apply match with Device green_2 us224_1 MODE apply Request Group rqgroup3 Device Group dgroup22 registration units analog_audio_stream_in updated gt unavailable state update term bit_resolution maps gt state adc_resolution new value system bit 16 amp retained value system bit 16 state update term data_channels maps gt state adc_channels new value system integer 2 amp retained value system integer 2 state update term sampling_rate maps gt state adc_sample_rate new value frequency hertz 4
250. m a similar check Where devices are found that have resources available matching is triggered and IO Composition notified on the appointed system remote local system remote connect check_for_available devices gt check_for_available devices multicast perform_match _ S l l L figure 3 8 system connect notes solid lines indicate sequences which occur whereas broken lines may happen depending on circumstances Handling of this event involves cooperating IO_ Discovery services adjusting records kept on the cluster of systems present and may include nominating a new match system Because more than one system may be connecting there are dynamics to be worked out concerning the new cluster Resolving these issues relies upon empirical investigation and has been left to a future implementation Hence we assume their resolution prior to the sequence indicated 66 3 6 4 System Disconnect A system disconnect event requires a teardown of a computer system s presence which means cancellation of all stored results involving another across the distributed system It arises when a device disconnects from an interconnect where a system is attached and its IO Discovery service determines that a device has detached but was assigned to another system The event sequence outlined in figure 3 9 covers composition related aspects of resolving a system detaching from a cluster It begins
251. m builds and maintains a record of proximal systems for matching purposes The need for context awareness is paramount in circumstances where devices are highly mobile and they are embedded in the surrounding environment We achieve that awareness at the lowest layers of software allowing maximum flexibility and consistency in dealing with devices 10O_Configuration The IO Configuration service prepares devices for operation and subsequent participation in composition Driver code is expressed in a form independent of a particular kernel or processor and integrated into device descriptions which are expressed independently from any interconnect IO Configuration extracts driver code from this device description The operating system no longer contains device drivers The kernel is required to implement a framework for driver execution where they can dynamically handle configuring and operating devices 143 1O_Composition The IO Composition service is tasked with distributed coordination of the match process It is linked back to discovery and configuration This service cooperates to conduct matching in any distributed context A dynamic determination is made of which system will conduct matching Participants are also determined dynamically as the process commences A single requester with a request requiring satisfaction acts as the process trigger A pool of devices is established and matching attempted when they have resources available
252. m to the distributed context Devices on separate systems are managed as if they were part of the same virtual system Microsoft Research s HomeOS presents a computer system abstraction where all devices appear to be connected to a single computer Dixon Mahajan et al 2012 This is embodied in the system management of the services exported by device drivers Devices are arranged in a tree hierarchy and subdivided into groups representing the physical spaces within a home Access control for devices is applied at the level of these groups Application requesters interact with a driver through services These service interfaces are referred to as roles with each role containing a list of operations The names assigned to roles are unique and imply semantics Applications are realised as software components and must provide a manifest describing the device services they require A manifest comprises mandatory and optional features Each feature is a set of roles with at least one that is required 33 As a contrast Platform Composition from Intel Research integrates standard computer systems laptop mobile phone connected across a network to support collaborative work Want Pering et al 2008 Pering Want et al 2009 They set out to compose device related resources on separate systems to enable them to act as a unified platform this being the abstraction By adapting the supporting computer systems ad hoc tasks can be performed u
253. n a device 133 Significance to composition The process places no constraints on how a device is described it searches their structural descriptions according to how a RQGroup is structured This permits flexibility in expressing association within a request and how satisfaction is to be achieved The search seeks to systematically match every RQGroup associated with the current request Where no correspondence is found the search is guided to try further DGroups from the selected device Iteration ceases where a DGroup cannot be matched from the selected device thereby returning a null match for the request Main steps involved 1 a DGroup from selected device becomes the target 2 the sub goal find a RQGroup match is tried using the RQGroup and DGroup 3 failure to find correspondence results in backtracking to select another DGroup to step 1 4 a satisfactory match is applied to the device by altering assertions in the database the match is added to the results and the next RQGroup chosen 6 where unable to satisfy using any of the device s DGroups iteration ceases amp a null match is returned for the request as a whole 7 furthermore any matches for RQGroups tried earlier in the list are removed from the device at this point Nn Note details of match removal during the process appears below under the sub heading speculative application of results Matching request goal The translation of the search guidance generates a
254. native composite_rqi Request rq1 Group rqgroup1 gt Device Group dgroup23 MF 28 Requester black_5 requester_1 gt Device red_1 imic2_1 Outlet outlet1 Alternative composite_rq3 Request rq5 Group rqgroup4 gt Device Group dgroup2 MF 26 Requester black_5 requester_1 gt Device red_1 imic2_1 Outlet outlet1 Alternative composite_rq3 Request rq4 Group rqgroup3 gt Device Group dgroup3 MF 26 174 Stage 4 Connect 3rd Device M Audio Audiophile USB The example continues with the Third Device a M Audio Audiophile USB connecting to a further computer system This system then connects to the distributed system which initiates the match process again Stage 4 Match Expectations e the 3rd Device forces re submission of outlets with partial matches from Requester 1 e available Devices includes 1st Device with parts available but precludes 2nd Device due to an existing match e highest priority request fails for 1st Device but 3rd Device satisfies e cancellation of an existing match with 2nd Device which frees resources e application of match to 3rd Device amp a threshold match no further re submission to Requester 1 for Outlet outlet1 Active Request Alternative composite_rq3 5Q Request Alternative List composite_rq1 100 composite_rq2 75 composite_rq3 50 composite_rq4 25 composite_rq5 20 gt gt gt try another Request Alternative composite_rql at priority 100 with Re
255. ncements from each other The principal approach though is for clients to search for device services by name using multicast SOAP over UDP on a local subnet Devices listen for these messages and respond with a service description back to the client when able to offer that service Alternatively when a device connects to a network it sends an announcement message using multicast By listening for such clients can detect available services without the need to probe Digital Living Network Alliance DLNA delivers media interoperability across a home network and utilises the concept of devices device services and control points as requesters Allegro Software 2006 Digital Living Network Alliance 2013 It is based on Universal Plug and Play UPnP Internet_Engineering Task Force 1999 Microsoft 2000 TCP IP using Ethernet IEEE802 forms the basis for all network connectivity It adds web standards HTTP HTML XML amp SOAP to provide a framework for device discovery device and services description control and presentation DLNA Discovery is based on the UPnP Forum Device Architecture UPnP 2008b When a new device is added to a network the service discovery protocol SSDP allows the device to advertise its presence to the network This message advertises its services and location of a description The number that must be sent varies according to the number of distinct embedded devices and services contained therein Due to the unre
256. nction To determine whether to discard a sub match as trivial we use an ad hoc uncertainty scheme to guide the search and use problem specific information to define it The requester is permitted to assign a factor as a qualification of certainty at desired points in a structural description Suitability of a sub match is determined by whether a summation of its certainties achieves a threshold value The requester specifies key points where a summation must reach an acceptance measure in order for the sub match to be included in the results For example a request for an audio codec seeking a module that can convert a signal from analog to digital could be expressed as a single task element module with 2 categories task amp control each comprising subcategories and aspects with sought after values A sample application of weightings and thresholds used during testing appears as follows task_element 0 141 task O 11 function 0 9 direction 5 ug us enum analog_to_digital sampling_rate 2 frequency hertz 48000 data_channels 1 system integer 2 bit_resolution 1 system bit 16 role O O principal 5 ug us enum convert control 0O 1 approach O 0O 1 operate 1 uq us enum required At the leaf level weightings are assigned sin
257. nd are used for driver code development and verification purposes For Devil from IRISA the interface represents the most minimal abstraction in the form of registers ports and device variables They are expressed as discrete terms which are tightly bound to hardware level concepts Merillon Reveillere et al 2000 The Termite project through device specifications models a software view of device behaviour as part of driver synthesis Device registers that are accessible to a driver are included as is device reaction to reads and write to them This reaction may include updating registers or generating interrupts It is derived from a register transfer level RTL description of device written in a Hardware Description Language HDL Ryzhyk Chubb et al 2009 26 The Singularity operating system uses a manifest presented as metadata to accompany driver code It is intended to simplify development of drivers by automating system resource configuration The manifest declares system resources required by driver code A minimal hardware abstraction refers to registers ports interrupt request lines IRQ and memory plus interconnect dependent terms Hunt and Larus 2007 Describing Hardware Interconnect Specifications Peripheral Component Interconnect PCI is representative of an interconnect that has evolved to be independent from any system design and allows for an expanded range of device attachment In the published specificat
258. nects In circumstances where devices are determined to be assigned to other systems then adjustments are made to the database of known systems An example of a physical connection topology where systems must be accounted for appears in figure 3 4 1M 10 9 figure 3 4 physical system connection topology example Note that additional systems have been included to form a cluster that is involved in matching From the perspective of computer system six in the above topology an indicative expression of the connections to other systems is contained in the following Prolog facts 51 system name accessed through device adjacent system name accessed through system system cs1 cs3 system cs2 cs5 system cs3 d2 adjacent cs4 cs3 system cs5 d7 adjacent system cs7 cs3 system cs8 cs10 system cs9 cs10 system cs10 d8 adjacent Of importance is distinguishing those systems adjacent to a computer system Where adjacency is the case the device typically an interconnect bridge is indicated as forming the interface to devices from other systems Where systems cannot communicate directly they are denoted as utilising an adjacent system as the gateway Computer system selected to conduct composition dynamic In the process of nominating a computer system to conduct composition a cluster of systems is accounted for and a record kept as outlined above Once a system is determined for matching a furthe
259. nents are constructed independently and must be logically integrated The process of installation is preceded by deciding which aspects of the house are to be automated This includes the selection and desired placement of components Following this the suite of control units are programmed to facilitate sensor input and control output according to the configuration The mobile phones and tablets are loaded with a control application and integrated with the servers Then settings are customised for the occupants This may include user defined control categories environmental settings and custom interface elements 1 2 Analysing the Example The example was chosen to show that how a device is to be used must be determined prior to installation It demonstrates the extent of setup required to create a distributed system within the context of a home This involves tailoring server configuration to enable devices to be controlled and linking input sensors and audiovisual feeds to particular input channels Then there is the installation of custom application software on control devices to permit them making any sense of the context It demonstrates an architecture where the operating system on the server mobile phones and tablets has no awareness of the devices used in the home Finally selection of devices and the specific control they accept is evident in audiovisual components and simple switch operations for other equipment In other words the sy
260. nge of devices Its descriptive power however is bounded by the choice to focus upon input devices The European Computer Manufacturers Association ECMA describe a set of devices as examples for a user interface taxonomy contained in their architectural model They present a categorisation for input then output devices which are detailed in figure 4 3 A definition of each is provided and select devices mentioned from existing systems The derivation of categories for input devices is based around types of interaction tasks namely selection position orientation path quantify text capture and image capture These terms find mention in earlier work on graphical user interfaces Foley Wallace et al 1984 The division of output devices is according to those of a static and permanent nature and others providing dynamic temporary output refer to ECMA User Interface Taxonomy TR 61 European Computer Manufacturers Association 1992 A input device taxonomy selection choosing from a set of alternatives e g mouse tablet light pen pen touch panel or screen joystick trackball keyboard eye tracker wheel glove gesture suit position indicating a location e g mouse tablet light pen pen touch screen joystick trackball keyboard eye tracker wheel glove gesture suit orientation orientation of an entity in a 2 or 3 dimensional space e g joystick keyboard glove gesture suit path generating a series of positions or or
261. nsist of 2 channels per device spread across 2 devices then settling for the least preferable of a single channel on each of 4 separate devices 4 5 3 Seeking Access and Needing to be Controlled An important aspect to meeting the challenges faced by distributed systems concerns reconfiguring device access in response to connection events Keeping the system as responsive as possible means establishing access through composition This includes automatic reconfiguration of participants as a result At the level of the structures being composed devices need to provide details of how they are controlled and where they require dynamic configuration A requester on the other hand needs to specify what they can control We discuss the way in which control is described at the level of modules in a device description before looking at how to accomplish automatic configuration of logical control Describing device control During the derivation of the taxonomy a category control was included to describe the way in which a device is operated expressed at the level of modules This is useful for conveying whether configuration is required or intervention is needed during operation Furthermore which commands are required their ordering and the source of control be that other modules or external direction A sample use of the control category by a task element module is described below It indicates that the module for muting the audio out stream is co
262. nsure composition can happen anywhere Lacking awareness of computer system events Existing approaches are characterised by a sense of disconnection to their operation What is happening on each computer system is separate from the distributed system This stems from awareness not being provided or deemed to be an area of concern The failure to percolate events up through intervening software layers rests with the operating system and middleware The events being talked about are generated on interconnects where a device connection or disconnection registers at the hardware level and is detected by all systems attached to that interconnect e g Firewire IEEE 1995b A lack of an equivalent mechanism in the interconnect used by existing systems means widespread awareness of any disconnections is problematic be they device or other systems To compensate for a lack of explicit awareness DLNA s discovery messages UPnP based include an expiration time and eventually expire on their own The only advice given for device disconnections is to re multicast a message and control point departure yields no action at all UPnP 2008b Similarly Jini attempts to compensate for being distributed by devices registering their services on a leased basis which times out meaning it requires explicit renewal Sun Microsystems 2003 An example of consistent linkage through to process initiation is the Bluetooth interconnect which implements hardware le
263. ntation OSDI 00 San Diego CA USA 189 Microsoft Corporation 2000 Understanding Universal Plug and Play white paper 06 2000 Microsoft Microsoft Corporation 2005 Web Services Dynamic Discovery WS Discovery specification Microsoft Microsoft Corporation 2006 Devices Profile for Web Services specification Microsoft MSI Computer 2004 KT6V ATX motherboard manual rev 1 1 MSI Newmarch J 2006 Foundations of Jini 2 Programming Apress ISBN 1 59059 716 8 NeXT Computer Inc 1993 NeXTSTEP Developer s Library NeXTSTEP v3 3 ed Addison Wesley ISBN 0201632519 Oliver R S Shcherbakov I amp Fohler G 2010 An Operating System Abstraction Layer for Portable Applications in Wireless Sensor Networks In Proceedings of the ACM Symposium on Applied Computing SAC Sierre Switzerland DOI 10 1145 1774088 1774243 pp 742 748 Oney W 2003 Introducing Windows Driver Framework viewed March 2014 lt http www wd 3 com archive FrameworkIntro htm gt Open Firmware Working Group 1996 Open Firmware Recommended Practice Generic Names report v1 4 OFWG OpenHCI 1997 Firewire 1394 Open Host Controller Interface Specification v1 00 Promotors of the 1394 OpenHCI OpenHCI 2000 Firewire 1394 Open Host Controller Interface Specification v1 1 Promotors of the 1394 OpenHCI Panic I 2013 The Lightning Digital AV Adapter Surprise viewed March 2014 lt http www panic com blog 2013 03 the
264. nted system 3 6 2 Device Disconnect A device disconnect event requires a teardown of its presence which mean systematic cancellation of all stored match results involving the device across the distributed system The event arises when the IO_Discovery service determines a device has disconnected from an interconnect where the system is attached that had been assigned responsibility for it The event sequence outlined in figure 3 7 begins with IO Discovery passing notification to IO_ Configuration to remove the device Io p aD a Eo device remote disconnect device_remove cancel_all tee involving_device cancel_all_matches_involving device multicast cancel_match_from_device LK 7 gt permatch cancel_match_from_requester _ S permai perform_match gt gt H requester_ remove ol i Beets a 1 device_remove L i remote remote remote J erman cancel_all_matches_involving_device ia cancel_match n_fom_requester aT per match mie 1 4 figure 3 7 device disconnect notes solid lines indicate sequences which occur whereas broken lines may happen The computer system indicated by the shaded area is the one assigned responsibility for the departed device and the boxed areas are services on the same system Removal commences by advising IO Results to cancel all matches invol
265. ntrolled externally through a command sent from the computer system which is permitted during configuration or operation 108 task_ element task i ul function il 1 011 data_ format e OS Hl ENN uq us enum digitall signal_mute system boolean true role 1 1 1 principal ug us enum adjust controt 1 commands 1 1 response uq us enum none state_change uq us enum audio_out_mute command uq us enum set_audio_out_mute link uq us enum TE USBControl source uq us enum external temporality ug us enum all fapproach command_queue_size system integer enum 1 configuration_sets uq us enum adjust_mute operation_sets ug us enum adjust_mute command_ordering ug us enum no_ordering operate ug us enum required configure ug us enum required meee eo mma With appropriate process support it would be possible for a requester to utilise this information to fine tune guidance on how to control modules This includes when or if control is required in circumstances where configuration is fixed In fact introspection is a technique that could be used to build a comprehensive picture of a device s control requirements Although reflec
266. o digital ADC signal conversion digital audio I O and mute capabilities for all signals There is also MIDI I O plus analog signal controls associated with the user interface Internally the device organisation comprises a range of integrated circuits that roughly equate to the signal conversion capabilities ADC DAC plus digital I O Asahi Kasei Microsystems Co 2004 Cirrus Logic 2005 Except that the device also includes a generalised microcontroller core to handle streaming audio I O across the USB interconnect and other unspecified functionality Texas Instruments 1999 Consequently our focus is on generating a logical representation of a device and accounting for its functionality from an external perspective This is because we are concerned with facilitating access to control interfaces for a device Hence what matters is its exported functionality viewed from the perspective of a requester Device description To complete a structural breakdown of a device there is an obvious requirement for complete information to be accessible The sort of details contained in the sources mentioned range from product datasheets through interconnect specifications to operating system requirements These are assumed to be accessible and open for referencing Building a description of a device is a matter of elucidating the significant modules in roughly the following order i targeting the main task elements to describe functionality 11 in
267. oblem occurred and restart 40 2 5 Requirements of a System Our examination of existing work in distributed systems reveals significant issues exist at each stage of the process Before proposing means of resolving these shortcomings we identify key trends that are changing the context within which distributed systems operate A series of technical requirements are arrived at by systematically addressing the issues and considering the trends 2 5 1 Trends and Contexts Trends Affecting Distributed Systems Others have argued that distributed systems are undergoing a period of significant change due to a series of influential trends Geihs 2001 Satyanarayanan 2001 Coulouris Dollimore et al 2012 In broad terms these consist of i pervasive networking computer systems becoming embedded in the surrounding environment 11 ubiquitous amp mobility highly mobile computer systems encountering variable connectivity iii multimedia services delivery of audiovisual data that requires quality of service guarantees iv distributed systems as a utility logical services exported for remote use The collective impact of these trends is they compound the shortcomings identified in each stage of the process Pervasive networking means there are a greater number of devices to discover Ubiquity and mobility force composition to be more frequent to account for the system being more dynamic However if devices are described using named
268. ocates an interrupt connected to a PCI interrupt pin Memory Device memory subsystem SMBus 1 0 or 2 0 Host Controller Smart Battery Subsystem power source 30 AC Device power source Module Device bus node General Purpose Event GPE Block Device Processor Device Ambient Light Sensor Device I O Advanced Programmable Interrupt Controller APIC or I O SAPIC Device e Additional devices not assigned IDs ATA IDE serial ATA SATA controller floppy controller USB port capabilities PC AT real time clock RTC CMOS e Display Adapters ACPI Extensions for Describing Hardware Operating System Driver Development Kits The first of two operating systems examined is Apple s Mac OS X which is targeted at their own custom designed system platform Driver code development is handled by an object oriented framework referred to as the I O Kit which provides a runtime environment for handling drivers Apple 2007 The I O Kit draws a distinction between devices and interconnects treating both as devices but distinguishing an interconnect as capable of device attachment The principle organising concept is that of a device family which represents an abstraction of common functionality for devices of a particular type The I O Kit families from interconnects through storage to human interface devices are outlined in figure 2 12 ADB Apple Desktop Bus Firewire FireWire DV ATA and ATAPI digital video z Audio FireWir
269. ock The motivation behind the changes required for this service is alleviation of dependencies A key one that devices have upon a computer system concerns interconnect specifications Implied by the design of a device is adherence in full to the specification for the interconnect it uses to attach We acknowledge fundamental characteristics defining how a device connects such as the mechanical structure of connectors power consumption and electrical signaling This extends to providing an indication of system requirements from interrupts resources memory reservation through to power requirements All warrant articulation to facilitate configuration However their logical structure does not need to be interconnect specific We require the definition of a device identity block to be independent of any interconnect Keeping this block opaque to any interconnect specification alleviates 54 problems with requiring an understanding of them to decode its structure In fact logical visibility of device structures from an interconnect need only include reference to the data block location 3 3 4 Requirements of Device Descriptions Indicate system resource requirements static and their allocation dynamic Providing an indication of system resource requirements is necessary to permit devices that are deployed separately to be configured for operation Whether these system resources are interrupts memory allocation or reservation their express
270. ode assigned to that device IEEE 2000 170 Lastly an interconnect determines how a device is identified At the very least this means determining locality but may extend to resolving uniqueness and include some sort of determination of device type Firewire provides a means of determining locality through dynamic assignment of logical node and bus numbering for all attached devices A separate centralised means of determining uniqueness is handled through assignment of a EUI 64 code for vendor determination and to distinguish their products as indicated in the bus information block shown The specification also dictates type by reference to fields in a persistent data block where named properties and values indicate device attributes refer to the structure of configurationROM IEEE 1999 3 Device Dependency Upon Platform Configuration Code Once a computer system is powered on a bootstrapping operation is performed by platform configuration code to enumerate all devices attached to a computer system In the case of those systems incorporating a PCI interconnect such as PowerPC Common Hardware Reference Platform CHRP this is realised as interconnect accessible registers being consulted then updated as each device is enumerated Apple IBM et al 1995 The process involves distinct steps beginning with the introspection of devices during bootstrap to establish whether they have any logical requirements When conducted as a software
271. of driver structure and device accesses to improve correctness Williams Reynolds et al 2008 This has been taken further in Nooks by isolating drivers in a protected run time environment The aim was to prevent their faults crashing the entire system and permit restarting the driver after a fault Swift Annamalai et al 2006 These efforts collectively improve articulation of the driver kernel relation They have an indirect focus on a reduction in driver execution privileges which arises as a result of coping with their dependencies 6 Driver Code Dependency Upon Processor This dependency is static in terms of dictating a driver be expressed using a set of instructions including those for accessing device based structures The processor defined instruction set serves as the eventual target for driver compilation In its final form a driver contains a set of logical access types for i o operations and a view of memory in terms of endianness ordering of bytes for 16 32 or 64 bit words A fundamental constraint imposed by a processor is for a driver to be presented in an executable form This represents an architectural dependency requiring logical awareness of a target processor in order to perform compilation or translation Techniques are available for modifying when executable code is generated Firstly when code is compiled by employing multi architecture binaries with a suite of target processors contained in the code bundle ref
272. og IN to ADC RCA 12 Analog IN to ADC 1 4in 17 Digital OUT to DDC Out 17 Digital OUT 16 Digital IN from DDC In 16 Digital IN 15 Midi IN 15 Midi OUT 14 USB Isochronous IN OUT electrical interface EI 14 USB Port 12 Analog Audio IN 1 4in 12 Analog Audio IN RCA 11 Analog Audio OUT RCA 11 Analog Audio OUT Head Phone 17 Digital Audio OUT 16 Digital Audio IN 15 Midi OUT 15 Midi IN 18 Power Connector Match Conditions transform n a adjust USB Control transform n a adjust USB Control potentiometer potentiometer PCM Audio stereo analog audio stereo analog audio PCM Audio stereo analog audio stereo analog audio PCM Audio S PDIF PCM Audio S PDIF Midi Midi type B port connector 0 25in mono jacks x2 RCA jacks x2 RCA jacks x2 0 25in stereo jack RCA jack RCA jack 5 pin DIN 5 pin DIN 2 5mm jack e associated with adjusting settings for ADC DAC amp DDC In DDC Out 16 bit 44 1kHz 24 bit 44 1kHz 24 bit 48kHz 24 bit 96kHz Device Code Interfaces DCI Digital to Analog Converter select sample rate resolution channels Analog to Digital Converter select sample rate resolution channels DAC Mute set mute on off ADC Mute set mute on off DDC In Mute set mute on off DDC Out Mute 151 set mute on off 4 in 4 out channels 4 in 2 out or 2 in 4 out channels 4 in 2 out or 2 in 4 out channels 2 in or 2 out channels Registration Units
273. on channels set master mute on or off adjust left right volume up or down x1 attached to TE ADC x1 attached to TE DAC sample rate 48kHz resolution 16 bit channels 2 sample rate 48kHz resolution 16 bit channels 2 0 dB 0 dB off 148 Device Logical Overview sampling rate left volume master mute resolution right volume y channels y Mute a0 DAC Out Volume TE LE TE Ey adjust convert adjust par Audio PCM usg USB Stream Fom Port IN OUT IN OUT PCM audio USB Control kfm E gt module key task element electrical interface user interface communications link audio ADC Gain ft aE a Ely audio amp A rate MI ee or LINE resolution channels UT MIC LINE Switch control requirement v registration unit amp device boundary e EE figure A 2 Griffin iMic v2 device structure 149 Audio OUT mini stereo socket Audio IN mini stereo socket A 1 2 M Audio Audiophile USB The M Audio Audiophile USB device is classified as a stereo audio codec MIDI interface with digital IN OUT It is described minimally in the user manual supplied with the product M Audio 2006 The device manifests as indicated in figure A 3 1 4 headphone headphone main output MIDI power jack level level 170 button USB coaxial S PDIF coaxial S PDIF RCA RCA 1 4 unbalanced port output input output input inputs figure A 3 M Audio Audiophile USB device front and back view
274. on matched value q us enum external A term device boundary matched value syst m boolean true C SC term relation C SC term Logical_structure A term signal ended matched value uq us enum unbalanced A term data_format matched value Pe us enum tanalog A term connection establish matched values lees enum hot pluggable ept subnatch match factor check 4 gt term electrical sc term characteristics A term classification matched value ug us enum external A term classification matched value uq us enum external HEHHEHE ETE ETHEL HHHH HHHH EE ETE ETE TEETH ETE TEETH EP Et ttt checking have an acceptable RQGroup match comparing match factors is 26 gt 42 ERROR no match found for RQGroup rqgroup1 with Device green_2 us224_1 reversing application of group matches so far with same device aborting Request List at rq1 amp returning null match X checking have derived a match for Request rq1 ERROR no match found for Request rq1 reversing application of matches for prior requests with respective device s aborting Request Alternative composite_rql amp returning null match X checking have derived a match for Request Alternative composite_rql gt gt gt try another Request Alternative composite_rq2 at priority 75 with Request list rq2 rq3 next Request rq2 with RQGroup list rqgroup1 gt gt gt gt gt try another Device green_2 us224_1 next RQGroup rqgroup1
275. on of matches for prior requests with respective device s aborting Request Alternative composite_rq2 amp returning null match X checking have derived a match for Request Alternative composite_rq2 gt gt gt try another Request Alternative composite_rq3 at priority 50 with Request list rq4 rq5 next Request rq4 with RQGroup list rqgroup3 gt gt gt gt gt try another Device green_2 us224_1 next RQGroup rqgroup3 gt gt gt gt gt gt gt try another DGroup dgroup21 from Device green_2 us224_1 FHEHELEEELEP ETE PETE T ttt ttt ttt ttt ttt ttt ttt ttt ttt HEHHEHE HHHH HHHH HEEL EET ET EE EET EET EEE ETE EEE TEETH EEE TEE Et checking have an acceptable RQGroup match comparing match factors is gt 23 gt gt gt gt gt gt gt try another DGroup dgroup22 from Device green_2 us224_1 HEHHEHE HHHH HHHH HHHH HHHH EEE ETE ETE TEETH EEE TEE EEE PEt tte gt checking availability of Registration Unit analog_audio_stream_in available A term direction matched value uq us enum analog_to_digital A term sampling_rate matched value frequency hertz 48000 A term data_channels matched value system integer 2 A term bit_resolution matched value system bit 16 166 accept submatch match factor check 9 gt 9 M C SC term function A term principal matched value uq us enum convert M C SC term role M C SC term task accept submatch match factor check 14 gt 14 M C SC ter
276. on taken from the match result and supplying a mode apply or remove executeRegistrationUnitAdjust _ _ executeRegistrationUnitAdjust Mode Device RH RT registrationUnit Device RH Status registrationUnitAdjust Mode Status NewStatus insert updated amp delete old resource availability into or from database retract registrationUnit Device RH Status assert registrationUnit Device RH NewStatus executeRegistrationUnitAdjust Mode Device RT registrationUnitAdjust apply available unavailable registrationUnitAdjust remove unavailable available 5 2 2 Code Interfaces Motivation Our intention is for logical access to a device to be automatically established as a consequence of composition The low level to device abstraction embodied in the terms from our taxonomy is the key to making this possible Identifying logical control points in a structural description becomes a straightforward task of expressing aspects of control It is a matter of following up by tailoring driver code interfaces to accord with the device 120 description We are assuming though that a requester being able to pinpoint control is a logical consequence of having the capacity to describe form and functionality Illustrative example An example to aid in understanding the concept is a request for an audio codec that successfully describes the module responsible for converting digital audio to an analog signal The re
277. operator to check for existence of device term NewMatchTerm RQTermName OldTerm NewTerm B1 new device term may have choices for binding at branch level findall NewTerm NewMatchTerm TList reverseList TList TermList member NewTerm TermList check device resource availability at branch term deviceElements NewTerm DMC DSA DCI DRU checkRegistrationUnitAvail Device DRU B2 check correspondence at next level to derive submatch WalkRQGroup Requester Device NewTerm RQSubSpec SubMatch 0 SubMF B3 perform checking of submatch acceptance measure as per request annotations checkSubMatch SubMatch SubMF RQMF ExtraMF B4 evaluate match conditions as per request amp device annotations device _ Device DSpec _ executeMatchConditions Device DSpec SubMatch DMC B5 getRequesterSpec Requester Spec executeMatchConditions Requester Spec SubMatch RQMC B5 calculate acceptance measure for branch term add it amp submatch to results NewMF is ExtraMF MF SubMF B6 NewMatch RQTermName RQMC RQSA RQOCI DMC DSA DCI DRU SubMatch Match B8 WalkRQGroup Requester Device OldTerm RQGT NewMatch X NewMF Y WalLkRQGroup Requester Device OldTerm _ RQGT Match X MF Y Modules Categories SubCategories iterate on no result for current term WalkRQGroup Requester Device OldTerm RQGT Match X MF Y WalkRQGroup Requester Device OldTerm RQGH RQGT
278. or Request Group rqgroup3 involving Device Group dgroup22 from Device green_2 us224_1 match factor 26 apply match with Device green_2 us224_1 MODE remove Request Group rqgroup3 Device Group dgroup22 registration units analog_audio_stream_in updated gt available state update term bit_resoLution maps gt state adc_resolution 173 value system bit 16 with no retained state found state update term data_channels maps gt state adc_channels value system integer 2 with no retained state found state update term sampling_rate maps gt state adc_sample_rate value frequency hertz 48000 with no retained state found apply match with Requester black_5 requester_1 MODE remove code adjust_adc_settings Request rq4 Request Group rqgroup3 gt DeviceCodeInterface adc_configure set_sample_rate set_resolution set_channels data audio_in_settings Request rq4 Request Group rqgroup3 bit_resolution system bit 16 data audio_in_settings Request rq4 Request Group rqgroup3 data_channels system integer 2 data audio_in_settings Request rq4 Request Group rqgroup3 sampling_rate frequency hertz 48000 retracting existing match transaction done with cancelling pre existing match completing apply of new match removing shadowed state to complete apply with Device red_1 imic2_1 applying group match with Requester apply match with Requester black_5 request
279. or the search to bind to one or more devices in an unpredictable manner It could be that single RQGroups from a request match to separate devices where the requester dictates more than one RQGroup match is necessary for a request to adequately describe and thereby target a device Expression in terms of discrete requests allows the requester to control the granularity to the association of RQGroups with particular devices It also allows alternatives to be specified which may span multiple devices by them being specified as separate requests Allowing control over matching to particular devices at the same time as permitting span across multiple devices is about improving satisfaction That is providing guidance for the process on how to match a particular alternative in terms of domain specific objectives Significance to composition The process places no constraints on the presentation of devices it investigates their suitability according to how a request is structured This permits flexibility in how requests are to be satisfied by a pool of devices The search seeks to systematically match every request associated with the current alternative Where no correspondence is found with the current device the search is guided to try further devices Iteration ceases where a request cannot be matched to any device in the pool thereby returning no match for the alternative Main steps involved 1 a device from the available pool is selected as the t
280. orm match wrap up 4 1 Buxton s taxonomy of continuous manual input devices 4 2 Card s Input Device Taxonomy 4 3 ECMA User Interface Taxonomy 4 4 Performance Characteristics for Communication Channels 4 5 input output model of the human senses 4 6 PCI elaboration of engineering specifics 4 7 Smotherman s sequencing based i o taxonomy 4 8 Miller s Systems Task Vocabulary 4 9 category subcategory decomposition into aspects aspect values 4 10 i o taxonomy 5 1 audio channel strip arrangement for Tascam US 224 audio device A 1 Griffin iMic v2 line drawing A 3 M Audio Audiophile USB device front and back view A 4 M Audio Audiophile device structure A 5 M Tascam US 224 device front and back view A 6 Tascam US 224 device structure 14 29 33 49 51 51 57 64 65 66 67 68 69 70 70 T1 78 79 80 81 82 85 86 96 97 135 147 150 152 153 155 B 1 distributed system implementation activity related to connection events 160 B 2 distributed system implementation activity related to the match process 161 xiii xiv 1 Introduction Establishing access to input output i o devices across a distributed system presents a problem and poses significant challenges worthy of investigation For effective use of devices in a distributed system they must be managed by software that enables access to exported functionality in a reliable and consistent manner The problem is that significant
281. ose chosen arbitrarily for inclusion with their development environment Apple 2007 Likewise development under Microsoft s WDM exhibits complexity due to the failure of kernel to provision fault tolerance This leads to drivers being expected to implement recovery actions such as orderly cancellation of i o operations Oney 2003 Attempts to bridge the gap between realisation and requirements resulted in the Uniform Driver Interface specification Project UDI 2001a Project UDI 2001b This effort sought to encapsulate common driver functionality inside a portable environment which would require limited interfacing for each kernel Although promising the reuse of core functionality for a particular driver the engineering required results in complexity at the point where the environment interfaced to the kernel This is illustrated in figure 2 7 for a UDI based driver for the USB interconnect Application Code UDI USB interface OpenUSBDI UDI kernel interface UDI Logical Device Drivers Core Functions USB driver interface USB Device Driver USB Host Controller Driver OHCI UHCI USB Host Controller figure 2 7 overview of a USB driver for UDI framework coloured area represents the encapsulated environment for a generalised USB driver with the lower layers interfacing as required for each kernel USB_Implementors_Forum 2000 The handling of drivers
282. ossible where types are denoted exclusively by names This is because knowledge of device properties is 74 implied by such references Difficulties with their articulation for use during composition stem from their inaccessibility and a lack of consistency Properties are defined in published specifications for interconnects and device datasheets but they are inconsistently provided with logical visibility The absence of a full account of them combined with a lack of consistency to those that are accessible restricts composition to matching named types Any properties articulated are referenced only by driver code when configuring and operating a device Interface Definition Languages demonstrate the utility in expanding description by specifying logical access to hardware and communication with a device Device interface specifications articulate key properties ports registers amp device variables which are used to generate driver code stubs to operate a device e g Devil IDL Reveillere and Muller 2001 Functionality is formalised as a series of events for later verification of code and a specification developed by modeling device behaviour from the perspective of a driver e g Termite project Ryzhyk Chubb et al 2009 Both approaches validate a link between formal specification of device properties and more effective realisation of logical control However they advocate no change to composition Virtual Machine Monitors VMM p
283. outs as repeating or single shot and timestamps for measuring elapsed time UDI also defines an interface to provide a driver with the ability to record information during operation in the form of tracing and logging functions The trace data is intended for debugging use expressed in terms of trace event classes common metalanguage specific through driver specific and the logging of data describing infrequent events state of an operational system refer to chapter 14 on timer services Project UDI 2001a Project_UDI 2001b Fault likelihood An indication of the tolerances underpinning device operation is relevant to data persistence Returning to the example of differing storage technology attached via an ATA interconnect both have reliability and error estimations calculated by the manufacturer that pertain to data integrity The flash memory based technology provides an indication of how many times data can be written before it can no longer be read reliably Whereas hard 90 disk estimations are for both read and write access based on consideration of it being mechanical as well as a magnetic recording Estimates of fault free operation represent properties of a device that are determined during manufacture They are published in product manuals for reference purposes and list features such as reliability or data integrity These are expressed as load unload cycles and non recoverable read errors in units of time or related concep
284. owever utilises a RS 232 C serial and the other a USB interconnect The former transfers data at a rate of 18 1200 bits per second and employs a system interrupt per single byte transferred It uses ports from i o space to read successive bytes received from device USARSystems 1997 The USB version transfers data in the form of discrete packets at rate of up to 1 1Mbps to a buffer with system memory A system interrupt is generated once multiple bytes have been sent from the device STMicroelectronics 1999 Compaq Hewlett Packard et al 2000 5 Driver Code Dependency Upon Kernel Code This dependency can be characterised statically in terms of structure definitions as well as dynamically by the manner in which a driver interacts with the kernel In particular the code structure of a driver is defined by the kernel The nature of such being an executable unit means it must comply with requirements set down by the target operating system This includes managing driver lifecycle within the runtime environment and provisioning system resources required for the driver as distinct from the device The manner of access to the kernel is specified for allocation control and arbitration of logical resources for driver and device during operation Broad reliance upon a particular kernel is due to more than just the driver being a unit of executable code It is tailored for a particular purpose During configuration a driver s external refer
285. pendent deployment of computer system elements occurs by stipulating where services must be located At the same time to build a picture of a what a redefined approach to computer system design constitutes The IO Composition service is tasked with configuring access to devices across a distributed system It is linked to the low level code for enumerating and discovering devices As such it must be present alongside the other services to ensure robustness and responsiveness We made adjustments that affect the deployment of the service and redefine the concept of a system platform The IO Composition service is required to be embedded with the core of each computer system and forms an integral part of a processing module for a computer system 61 3 5 Support Services Further services provide support to IO_Discovery IO Configuration and IO_Composition on each computer system They are part of a clear separation of duties that contributes to a simpler design Defining these requirements is also part of distinguishing i o related services from other system software Each support service manages a particular aspect of the distributed system be that requesters match results external access points containing requests or device resource availability 3 5 1 IO_ Resources The JO_Resources support service is responsible for managing the allocation of device resources for those assigned to a computer system It also receives notifications to est
286. point and deriving the sub match not attempted This has the added benefit of forcing consideration of additional elements of a device where resources have already been allocated 119 Implementation specifics The implementation references resources by associating them with the branch term for example appearing with task category inside the 4th square bracket in a structural description as follows LL task_element te3 1 dac_configure task audio_stream_out function 0O 1 The reference to audio stream_out resource is used by the process to check facts recording current availability registrationUnit device1 audio_stream_out available registrationUnit device1 audio_stream_in unavailable Goal expression During the traversal of a structural description in the goal WalkRQGroup refer to the section guiding the search for elaboration a check for resource availability is made prior to deepening the search The goal checkRegistrationUnitAvail is tried using the list taken from the annotation mentioned above checkRegistrationUnitAvail _ checkRegistrationUnitAvail Device RUH RUT registrationUnit Device RUH available checkRegistrationUnitAvail Device RUT At the end of the process when applying or removing a match result the facts associated with resource availability are modified by trying the executeRegistrationUnitAdjust goal with the annotati
287. presence and co deployment is the best option In fact we go further in requiring driver code be embedded within a device description on each device The IO Configuration service with knowledge of the structure of a device description can prepare driver code The protocol for performing device configuration is detailed below Embedding driver code with an interconnect bridge device also targets a dependency driver code has upon the interconnect specification concerning access specifics Alongside the driver implementing functionality pertaining to a device distinct blocks are currently required to have interconnect awareness This is to access specific structures and details of how to perform control and communication Where drivers are guaranteed to be present and operational their development becomes simpler and a cleaner separation of responsibilities is possible Driver code compilation to virtual processor assembler A fundamental constraint for driver code is to be presented in an executable form This requires awareness of the target processor in order to perform code compilation The 55 dependency constrains code to be expressed in its final form where there is a specified manner of logical access for i o operations and an established view of system memory Leaving operating system development environments to ensure correctness shifts the constraint without addressing the problem The dependency needs to be removed otherwise drivers
288. pt submatch match factor check 6 gt M C SC term channel M C SC term primitives accept submatch match factor check 12 gt 9 M C SC term communications Link term paige matched value uq us enum adjust wec s termi M C SC term Ct efecktng availability of Registration Unit analog_audio_stream in available A term configure matched value uq us enum required M C SC term approach M C SC term control A term principal matched value uq us enum adjust M C SC term role M C SC term task A term data_format matched value uq us enum digital A term signal_mute matched value syStem boolean true M C SC term function A term principal matched value uq us enum adjust M C SC term role M C SC term task A term configure matched value uq us enum required A term operate matched value ug us enum required M C SC term approach M C SC term control accept submatch match factor check 14 gt 10 M C SC term task element A term data_format matched value ug us enum Canalog A term Connection establish matchet dataa Hua aS aun hot _pluggableJ accept submatch match factor check 3 gt 2 M C SC term electrical M C SC term characteristics 165 A term direction matched value ug us enum input A term classification matched val Gee uns eeaGt A term direction matched re enum Tinput A term classification matched q us enum external A term si
289. q us enum required M c sC term approach M C SC term control term data_format matched value uq us enum digital A term signal_mute matched value system boolean true C SC term function A term principal matched value uq us enum adjust SC term role SC term task A term configure matched value uq us enum required A term operate matched value uq us enum required C SC_ term approach C t Spt Submateh Patch factor check 14 gt 10 SC term task element A term signal_ended matched value uq us enum unbalanced A term data_format matched value ug us enum analog term connection establish matched value uq us enum hot_pluggable cept submar eh match Factos Check SC term electrical SC term characteristics A term width matched value Clength mm 8 37 SC term physical_dimensions SC term physical_manifestation A term Connector matched value uq us enum rca_connector rca_connector A term classification matched value ug us enum externat A term device_boundary matched value syst m bodlean true M C SC term relation M C SC term logical_structure A term connector matched value _fug us enum rca_connector rca_connector A term classification matched value ug us enum fexternal A tera device Boundary matched value syst m boolean true C SC term relatio 8C term Logical structure A term width matched value
290. quest list rq1 next Request rq1 with RQGroup list rqgroup1 rqgroup2 gt gt gt gt gt try another Device green_2 us224_1 next RQGroup rqgroup1 gt gt gt gt gt gt gt try another DGroup dgroup21 from Device green_2 us224_1 HAHAHAHAHHA PETE PETE ETE Ett ttt ttt ttt ttt ttt tttttttttt ttt ttt HEHHEHE HHHH HHHH HHHH HHHH EEE EEE ETE TEETH ETE EEE TEEPE ttt et checking have an acceptable RQGroup match comparing match factors is gt 42 gt gt gt gt gt gt gt try another DGroup dgroup22 from Device green_2 us224_1 HAHAHHAHAHA HHHH HHHH HHHH HHH HHHH HHHH HHHH z eihtecking availability of Registration Unit analog audig stream in available A term direction matched value ug us enun anglog to_digital J A term sampling_rate matched value frequency hertz A term data_channels matched value system integer gt ie A term bit_resolution matched vali System bit 16 accept submatch match factor check 9 gt 9 M C SC term function A term principal matched value uq us enum convert M C SC term role M C SC term task accept submatch match factor check 14 gt 14 M C SC term task element A term direction matched value ug us enum unidirectional A term logical_channels matched value system integer aa A term signal_format matched value uq us enum digital A term model matched value _ ug us enum Cstrean accept submatch match factor check M C
291. quester is already aware of the parameters affecting the task of signal conversion sampling rate data channels bit resolution Hence this implies an ability to control the device via code interfaces associated with that codec Technicals Logical control points are indicated by branch level annotations of the structural descriptions associated with RQGroups and DGroups Those specified by a device indicate where driver code functionality accords with a structural description Whereas a request contains annotations at points where control is expected to be required During the match process code interface annotations are added to the results after a term and sub match are accepted including driver code interfaces Later when applying the results with the requester logical control points are verified to correspond Where agreement is found request annotations serve as a link to a table for managing external code interfaces Device annotations are used to select code interface headers included in the match results to populate the table thereby establishing access to a device Implementation specifics The implementation links to control interfaces in requesters through annotations at the branch level for example appearing with task_element module inside the 3rd square bracket in a structural description task_element Pall ladjust_adc_settings task 1 1 1 When applying the results with a req
292. r check 6 gt M C SC term channel M C SC term primitives accent submatch match factor check 12 gt 9 M C SC term conminications_link HEHHEHE ETE ET HHHH HHHH HHHH HHH HHHH HHHH checking have an acceptable RQGroup match comparing match factors is 12 gt 23 us enum uncompressed us enum pcm_audio gt gt gt gt gt gt gt try another DGroup dgroup23 from Device green_2 us224_1 FHEHHLEHELEP TEP HHHH itching availability of Registration Unit analog qudio_strean_out Ate rate matched value ug us enum required M c SC term approach M C SC term control A term direction matched value uq us enum unidirectional A term logical_channels matched value system integer 21 A term signal_format matched value uq us enum digital 1J A term model matched value ug us enum stream accept submatch match factor check M C SC term Link A term compression matched value A term data_format matched value accept submatch match factor check 6 gt M C SC term chanhel M C SC term primitives accept submatch match factor check 12 gt 9 M C SC term conminications_link HEHHEHE HHHH HHHH HEEL EEE ET EEE ETE ET EEE ETE ETE EEE TEEPE TEE Et checking have an acceptable RQGroup match comparing match factors is 12 gt 23 us enum uncompressed us enum pcn_audio ERROR no match found for RQGroup rqgroup4 with Device green_2 us224_1 reversing application of g
293. r record can be expressed in the database as match cs1 3 2 7 Changes to Computer System Specifications Service is embedded in a processing module and an integral part of system software Our intention is to target a context where independent deployment of computer system elements occurs by stipulating where services must be located At the same time to build a picture of a what a redefined approach to computer system design constitutes The IO_Discovery service is tasked with performing bootstrapping for a computer system It is the only low level code capable of enumerating permanently attached devices and constructing a record of them to hand to the IO_Configuration service As such it becomes the initial code to execute on a computer system and must be present when the system is powered on We made adjustments that affect the deployment of services and redefine the concept of a system platform The IO_Discovery service is required to be embedded with the core of each computer system further details regarding the deployment of services appears under the IO_Configuration service The IO Discovery service must also form an integral part of a processing module for a computer system refer to redefined platform specification discussion under IO_ Configuration 52 3 3 IO Configuration Service The JO Configuration service is tasked with preparing a device for operation on a computer system and participation in composition Devices
294. re 3rd ed Addison Wesley Reading MA USA ISBN 0 201 40993 3 Smotherman M 2000 A Sequencing Based Taxonomy of I O Systems and Review of Historical Machines In M Hill N Jouppi amp G Sohi eds Readings in Computer Architecture Morgan Kaufmann San Francisco CA USA pp 451 461 ISBN 1 55860 539 8 Stallings W 2000 Computer Organisation and Architecture Designing for Performance 5th ed Prentice Hall Upper Saddle River NJ USA ISBN 0 13 081294 3 STMicroelectronics 1999 Using the ST7263 for designing a USB Mouse datasheet AN1148 0699 Sugerman J Venkitachalam G amp Lim B H 2001 Virtualiizing I O Devices on VMware Workstation s Hosted Virtual Machine Monitor In Proceedings of the USENIX Annual Technical Conference Boston MA USA pp 1 14 Sun Microsystems Inc 2000 Jini Device Architecture Specification Specification version 2 0 Sun Sun Microsystems Inc 2003 Jini Architecture Specification specification version 2 0 Sun Swift M M Annamalai M Bershad B amp Levy H M 2006 Recovering Device Drivers ACM Transactions on Computer Systems vol 24 4 DOI 10 1145 1189256 1189257 pp 333 360 Szyperski C 2003 Component Technology What Where and How In Proceedings of the 25th International Conference on Software Engineering ICSE 03 Portland OR USA pp 684 693 Taos 1994 Taos Operating System Developer s Edition ver 1 28 TEAC Corporation
295. requirements of device descriptions The full range of requirements are as follows with the targeted constraint indicated in italics i changes to interconnect specifications e embedded device description in device identity block device dependency upon interconnect specification ii requirements of device descriptions e indicate system resource requirements static amp allocation dynamic device dependency upon interconnect specification e link device description to driver code e embed driver code with device device dependency upon driver code specific driver code dependency upon interconnect specification e driver code compilation to virtual processor assembler driver code dependency upon processor iii protocol definitions e device configuration procedure for use by driver code device dependency upon driver code iv records maintained e translation table for virtual to native code static driver code dependency upon processor v changes to computer system specifications e define a processing module as the core of a computer system device dependency upon platform configuration code amp processor e service embedded in a processing module and an integral part of system software device dependency upon platform configuration code amp kernel code e define kernel interface for driver code use driver code dependency upon kernel code 3 3 3 Interconnect Specification Changes Embedded device description in device identity bl
296. resolution and rate refer to DAC input characteristics Asahi Kasei Microsystems Co 2004 Alternatively the Analog to Digital Converter takes an analog signal as input This is characterised as a single ended voltage input and the signal has a particular voltage and impedance There are 92 further characteristics which may be used related to noise and distortion refer to ADC input characteristics Asahi Kasei Microsystems Co 2004 6 Properties related to finer grained description The distillation of categories begins with identifying communication links as another distinct element of a device Characterising links between internal elements and exterior features creates a range of properties By including analog signals as well as the digital this further extends the range of descriptive qualities Decomposition into elements necessitates a structure that accounts for the connections between them A further property is to provide logically accessible descriptions preferably in a human readable format Expressed as a series of terms charactering these properties they break down as i communication links link signal format direction synchronous transmit order channels acknowledgement channel data format rate block width encryption compression encapsulation ii logical structure connection relation iii information description specification task domain dictionary 93 4 3 Building an I O Taxonomy In the p
297. revious section device properties were sourced from interconnect specifications device datasheets platform specifications device driver development frameworks through to work in human computer interaction We captured a rich description of device form and function which forms a language of input output Property selections were made with a view to integrating them into a structured taxonomy In this section the sort of problems encountered by past classificatory efforts are discussed and an indication provided of how we intend to address them A structured taxonomy is proposed that goes beyond mere description by being a framework of related properties and representative of a wide range of devices 4 3 1 Problems Encountered Compiling Taxonomies Prior to constructing our own classification scheme we draw upon the perspective gained in prior taxonomic work to avoid making similar mistakes The sort of problems encountered in preparing a taxonomy are broadly identified by Fineberg Fineberg 1995 as i semantics ii level of detail iii conceptual basis and iv measurability An outline of each appears under the sub headings below and an outline for improving the methodology used to classify devices Semantics Reference to semantics is about the development of unifying dimensions and a well defined descriptive vocabulary where comparisons are possible across taxonomies In approaching the process of compiling a taxonomy we are able
298. rincipal matched value uq us enum adjust C term role C term task pr aGhecking availability of Registration Unit analog audio stream_out A term configure matched value uq us enum required C term approach C term control A A C A C C A A term data_format matched value uq us enum digital term signal_mute matched value system boolean true term function term principal matched valu term role term task term configure matched value uq us enum required term operate matched value uq us enum required M C SC term approach M C SC term control accept submatch match factor check 14 gt 10 M C SC term task element A term signal_ended matched value ug us enum unbalanced A term data_format matched value ug us enum analog A term conn ction_establish matched valu u us enum hot_pLuggable accept submatch match factor check 4 gt 2 M C SC term electrical C SC term characteristics term width matched value length nm 8 3 term physical_dimensions A sc l C SC term physical manifestation A uq us enum adjust term connector matched value uq us enum rca_connector rca_connector term classification matched value L q us enum external A term device_boundary matched value syst m bodlean true M C SC term relation M C SC term logical_structure A term connector matched value ug
299. ription according to association Logical representation of a device Although the taxonomy hierarchically relates terms and provides considerable descriptive power there is a need to establish what is being represented by a device description We could try to mirror a device s physical organisation and thereby approximate its layout in a similar manner to an electronic circuit Considering form this could be guided by the physicality of the device but functionality has a problem Because functionality is realisable in multiple ways detailing the physical is an unreliable guide to exported functionality It is the exported component which is being sought by a request A couple of examples illustrate this point Firstly the Apple Lightning AV adapter physically appears as a ARM processor based system on a chip connected to 2 exterior ports yet functionality wise it is a simple converter of data packets Lightning serial interconnect into a dedicated stream HDMI compliant video and audio Panic 2013 Another example which clarifies the distinction between exported functionality and physical organisation is the M Audio Audiophile USB audio device that connects to a computer system via the USB interconnect M Audio 2006 Externally the box has a range of audio I O ports both analog and digital plus MIDI I O further details are provided in the appendix The implemented functionality can be described as digital to analog DAC and analog t
300. rmine a pool of available devices and submit their structural descriptions invoke the match process to find a solution which satisfies the constraints 4 apply the results back with both requester and device s matched to configure access and update resource availability 0S The core resides with step 3 and involves elements from a requester and pool of devices Specifically the broad steps required to provide satisfaction break down as 113 e find a match for a requester s external access point do so by e select request alternative from the list associated with the external access point e systematically match the current alternative s list of requests do so by e for each request try a device from the pool of those available e systematically match the current request s list of RQGroups do so by e for each RQGroup try a DGroup from the current device e check for acceptable correspondence between the structural descriptions associated with the RQGroup amp DGroup Checking structural correspondence Establishing correspondence involves traversal of the structural description associated with a RQGroup and checking for correspondence with a device Being systematic involves iterating through the list of modules in a structural description and recording correspondence in the results The steps involved are 1 determine start term using both RQGroup amp DGroup 2 a match is tried using the start term amp list of modules from the
301. rocess concludes the results are applied back with the device to update resource availability and with the requester to configure access A pre existing match may have been improved upon and needs to be cancelled with the requester Where this happens a positive change in resources triggers the process again 3 4 2 Implementing the IO _ Composition Service We are concerned with automatically establishing access to devices across a distributed system This necessitates changes to implement this service These consist of requirements upon the process itself and adding to those upon device descriptions A distributed protocol for conducting the process is defined and changes proposed to computer system specifications The full spectrum of adjustments are as follows i requirements of the match process e structure match results for remote application ii requirements of device descriptions e indicate device resource availability dynamic iii protocol definitions e determining participants preamble e application of results wrap up iv changes to computer system specifications e service embedded in a processing module and an integral part of system software 59 3 4 3 Requirements of the Match Process Structure match results for remote application In circumstances where the application of results is likely to be remote from the other participants and from the computer system where matching was conducted the structure of results become
302. rom participants on that system Across a match cluster they form a dynamic picture of all active communication links Results can be removed as a symmetric operation to applying them by simply reversing the actions and order of their application As this service receives notifications to cancel matches reference is made to stored records and reversal proceeds Where system disconnections occur cancellation may involve multiple results Either way cancellation of matches with requesters becomes a trigger for composition 63 3 6 Event Sequencing Particular sequences of events arise on a computer system that are significant to establishing access to devices across a distributed system These involve devices connecting or disconnecting other systems connecting or disconnecting requesters arriving or leaving and initiating the match process Collectively the event sequences outlined in this section provide an illustration of what is required to manage a distributed system They also demonstrate the level of service integration required to construct and maintain a distributed system Each of the event sequences shows the way in which the main and support services are linked Having made the decision to automate configuring access this impacts most events with them concluding by initiating composition This is done to avoid communication links becoming unreliable following connects or disconnects When considering services cooperating acro
303. rosoft NEC ST Ericsson amp Texas Instruments Inc 2011 Universal Serial Bus USB 3 0 Specification standard rev 1 Hewlett Packard Hewlett Packard Inc Intel Corporation Inc Microsoft Corporation Phoenix Technologies Inc amp Toshiba Corporation 2009 Advanced Configuration and Power Interface Specification standard 4th ed Intel Corporation Inc Denver CO USA Hopper A 1990 Pandora an experimental system for multimedia applications ACM SIGOPS Operating Systems Review vol 24 2 DOI 10 1145 382258 382788 pp 19 34 Hunt G C amp Larus J R 2004 Singularity Design Motivation technical report MSR TR 2004 105 Microsoft Research Seattle WA USA Hunt G C amp Larus J R 2007 Singularity Rethinking the Software Stack ACM SIGOPS Operating Systems Review vol 41 2 DOI 10 1145 1243418 1243424 pp 37 49 HyperTransport 2008 HyperTransport I O Link Specification standard rev 3 10 HT Consortium IEEE 1995 Firewire P1394 Standard for a High Performance Serial Bus draft 8 v4 IEEE Piscataway NJ USA IEEE 1999 P1212 Draft Standard for a Control and Status Registers CSR Architecture for microcomputer buses draft 1 0 IEEE New York NY USA IEEE 2000 Firewire P1394a Draft Standard for a High Performance Serial Bus Amendment draft 5 IEEE New York NY USA 187 IEEE 2001 IEEE 802 Standard for Local and Metropolitan Area Networks Overview and Architec
304. roup matches so far with same device aborting Request List at rqg5 amp returning null match X checking have derived a match for Request rq5 ERROR no match found for Request rq5 167 reversing application of matches for prior requests with respective device s apply match with Device green_2 us224_1 MODE remove Request Group rqgroup3 Device Group dgroup22 registration units analog_audio_stream_in updated gt available state update term bit_resolution maps gt state adc_resolution restored value system bit 16 amp overwritten value system bit 16 state update term data_channels maps gt state adc_channels restored value system integer 2 amp overwritten value system integer 2 state update term sampling_rate maps gt state adc_sample_rate restored value frequency kilohertz amp overwritten value frequency hertz 48000 aborting Request Alternative composite_rq3 amp returning null match X checking have derived a match for Request Alternative composite_rq3 gt gt gt try another Request Alternative composite_rq4 at priority 25 with Request list rq4 next Request rq4 with RQGroup list rqgroup3 gt gt gt gt gt try another Device green_2 us224_1 next RQGroup rqgroup3 gt gt gt gt gt gt gt try another DGroup dgroup21 from Device green_2 us224_1 FHEHHLEHELE PETE PEt ttt ttt ttt ttt ttt ttt ttt tttttttttttt ttt HEHHEHE HHHH HHHH
305. rvice provider service K figure 2 15 Jini discover and lookup steps 1 device announces presence to find a lookup service 2 lookup service responds with proxy for later communication 3 device registers a copy with lookup service 4 client seeks to discover a lookup service 5 lookup service responds with proxy initially 6 lookup service responds to request with device service object 7 client access device service via downloaded object 38 Having found a lookup service during the discover process device services register and provide details of their service identity an object implementation and a set of service attributes A client request is a single or a set of services and is matched by consulting a lookup catalog The search is conducted using a service identity GUID or type If the GUID is unknown service type is used instead which is typically a list of classes representing service interfaces Then a series of attributes are checked where the value of each will generate an exact or ignored match The response returned to the client is in the form of matched service objects which enables the client to make method calls on a local object whilst being unaware of the distributed communication protocol Waldo 1998 Sun Microsystems 2000 Sun Microsystems 2003 Newmarch 2006 Process of Composition Access The intended consequence of composition is access to software encap
306. s Our approach separates qualitative expression from the units used to quantify them The intention is to employ qualitative terms to build the taxonomy and thereby avoid continual adjustments With the quantitative independent it can be extended through additions to the existing system of measurement An example of the sort of aspects and aspect values that could be utilised to quantify is the category communication detailed in figure 4 9 It is decomposed into subcategories of link and channel both of which may have a range of aspects associated with them Some of these values find expression as standard units or system units but others must resort to being an enumerated type enum 95 link_name UTF8 model unicast broadcast stream send_receive test_set acknowledgement no_ack ack reply signal format digital analog logical channels _ integer transmit order inorder out_of_order link transmit timeout ms transmit window integer initiation synchronous asynchronous blocking send true false oe direction unidirectional bidirectional communications segmentation roe false cancel pending true false channel_name UTF8 encapsulation unspecified interconnect specified lt specific gt compression uncompressed lt compression specified gt encryption symmetric asymmetric channel data format enum lt interconnect term gt data units pack
307. s and include those yet to be developed A taxonomy capturing the scope of form and function populates the description space with terms relevant to devices The description space is structured hierarchically to manage complexity A contribution is also made to improving the design and integration of operating systems components in particular those services responsible for managing devices from configuration through to composition and accomplishing such across a distributed system In this context configuration serves as a local system response to device connections ensuring they become operational then advertising their availability remotely Distributed composition services receive these notifications adding device descriptions to a database for use when matching requests We have adopted the language Prolog to describe devices and for implementing a distributed system It supports a database of device descriptions in the form of assertions and provides powerful support for matching via an inference engine The inference engine systematically examines a potentially large and complex search space for an acceptable extent of correspondence Requests can be expressed minimally as those elements of a device relevant to matching A consequence of this style of matching is the ability to allow requesters partial access to device functionality as a result of incomplete satisfaction Through awareness of the device domain the composition process handles al
308. s are already allocated ii knockout alternatives only request alternatives representing an improvement over any existing match will even be tried gt an existing match can only be replaced if it is improved upon as evidenced by the requester assigned priority to alternatives iii knockout alternatives a request alternative will be rejected when any of its requests fail to match gt an alternative must match all its requests otherwise it is not the alternative sought as a crucial request is missing one of a differing priority must be sought instead iv knockout requests a request will be rejected when any of its RQGroups fail to match gt a request must match all its RQGroups otherwise it is not the request sought with one missing v knockout RQGroups includes structural descriptions each RQGroup can only be satisfied by DGroups from the device which is bound to the current request gt a device description consist of a set of DGroups hence once a device is bound to a request the number remaining to be checked reduces vi knockout modules resource availability at the level of device elements determines whether a deeper search of a structural description proceeds gt where a sub branch is associated with a resource and recorded as unavailable it is skipped over amp a null sub match returned all without checking deeper 5 4 3 Managing Backtracking A further narrowing of the search is provided by managing the b
309. s important This is particularly relevant where we want to provide a highly responsive system and ensure that it is possible to recover from disconnections We can accomplish this by retaining results past their application to be referenced when removing a match The distributed context dictates that results must be expressed in a suitable form for communication back to the participants Furthermore by expressing them in a suitable manner results can be referenced to apply or remove a match and the operation performed on either requester or device 3 4 4 Requirements of Device Descriptions Indicate device resource availability dynamic In having the process of composition handle establishing access to a device we would like to avoid being constrained to apportioning them as a single unit This means device access gets expressed in terms of resources and how they are apportioned defines the scope of access Devices must provide an indication of resources and the extent of permissible access We stipulate that resource availability be articulated in an independently defined device description The IO Composition service with an understanding of the structure of a device description can extract and manage arbitrating access to resources then dynamically allocating them to requesters 3 4 5 Protocol Definitions Determining participants preamble The process is initiated as a result of changes in the availability of device resources across
310. s of meeting device access requirements whilst maintaining a robust distributed system This requires an approach that goes beyond a bespoke setup and static configuration Our goal is to build a distributed system with a capacity to endure along with the context which is long lasting potentially spanning many decades We intend to meet the requirements framing them as follows 1 capacity to describe and request devices from those known to new devices and ones not yet developed ii provide device awareness iii respond dynamically to devices connecting and disconnecting iv ensure devices are prepared for operation v match requests to devices through a process that results in granting access to them Addressing these would contribute to future proofing the system 2 1 1 Model of the Process Before continuing we define a distributed system as a cooperating set of computer systems for which the abstraction of a single logical system is created Its purpose is to share resources that are physically encapsulated within computer systems and can only be accessed from other systems by means of inter communication A computer system is typified by an organisation where access to or from the processor and memory is mediated through a device acting as a bridge A range of further devices attach to a shared interconnect originating from the other side of that bridge Stallings 2000 Devices are defined as a special type of resource that prov
311. sability Carroll and Kellogg 1989 The interface presented to the human user comprises elements of one or more devices Characterising the interface in a device description would provide the requester with the ability to specify those properties and have composition seek to satisfy such from the devices available A 76 series of HCI taxonomies provide an idea of the scope to interface properties Work in Virtual Environments extends the classification by referring to the sensory dimensions of interaction Refinement of these properties begins the process of deriving our framework Taxonomies of devices Notable early work towards classifying interfaces is Buxton s taxonomy of continuous hand controlled devices see also Foley s taxonomy Buxton 1983 Foley Wallace et al 1984 Baecker and Buxton 1987 It is intended to assist with finding equivalences and quantifying the generality of physical devices The taxonomy as shown in figure 4 1 is arranged according to the property sensed pressure motion or position and the number of dimensions 1 2 or 3 with a further sensing breakdown according to whether a mechanical intermediary is involved between the hand and sensing mechanism or the device is touch sensitive M or T Number of Dimensions 1 2 3 aan Tablet amp HA Isotonic 5 Rotary Pot Sliding Pot Tablet amp Puck Stylus iLight Pen Joystick 3D Joystick M i Vina a ERN G a a a ia oy
312. scription Named types not only denote functionality they point to descriptions that are located elsewhere Self description is about what else the device or its elements can describe about themselves in human readable form e g user manual For this information to be utilised or made reference to it needs to be logically accessible Embedding self description on a device to ensure locating them is straightforward and relevant to user operation of devices Yet existing examples provide restricted descriptions in the form of optional name strings that denote features For audio devices connecting to the USB interconnect allowance is made for optional strings for name fields in descriptors refer to Device Class Definition for Audio Devices USB_Implementors Forum 2006b Additionally there is the use of text strings corresponding to device features that are stored in a persistent data block Configuration ROM mandated by the Firewire interconnect refer to IEEE1212 CSR standard IEEE 1999 91 Logically relating elements together Decomposition into elements necessitates accounting for the structure of the whole device This means stitching them together to form a single entity by articulating the connections related to signal path or data flow Although what comprises an element remains unresolved it is sufficient to suggest that each has a property of connecting to or being related to others in some manner This is about describing interna
313. ser interface is returned to the requesting appliance The SpeakEasy approach at XeroxPARC Edwards Newman et al 2002 operates on the premise that at run time human users will be the ultimate arbiters that decide when and whether an interaction among compatible entities is to occur They expose users to device specific notions via custom objects in the form of mobile code that implements a user interface There is an assumed agreement between applications on mechanisms for acquiring and displaying a user interface but no knowledge of functionality underpinning user interface controls Platform Composition from Intel Research integrates computing systems to support collaborative work Want Pering et al 2008 Pering Want et al 2009 They set out to make device related resources on separate systems accessible to enable them to act as a unified platform Composition is explicit and involves the human user in connecting their existing platform services together using a graphical join the dots metaphor A Composition Framework tool is used to orchestrate system connections amongst devices Once services are made available through the operating system the framework is no longer involved Process of Composition Where and How The process of composition necessarily involves participants from across the entire distributed system Where it is conducted however may vary from being centralised to involving a set of systems or on all comp
314. settings Request rql Request Group rqgroup1 bit_resolution system bit 16 data audio_in_settings Request rql Request Group rqgroup1 data_channels system integer 2 data audio_in_settings Request rql Request Group rqgroup1 sampling_rate frequency hertz 48000 asserting new match transaction done applying match with both Requester and Device s Requester black_5 requester_1 Outlet outlet1 status flagged gt threshold gt MATCH PROCESS COMPLETED MATCH TRANSACTION Sectio narre sis fe A he eee A Requester white_4 requester2_1 gt Device green_2 us224_1 Outlet outlet1 Alternative composite_rqil Request rq1 Group rqgroup1 gt Device Group dgroup23 MF 28 Requester black_5 requester_1 gt Device blue_3 audiophile_1 Outlet outlet1 Alternative composite_rqi Request rq1 Group rqgroup2 gt Device Group dgroup11 MF 40 Requester black_5 requester_1 gt Device blue_3 audiophile_1 Outlet outlet1 Alternative composite_rqi Request rq1 Group rqgroup1 gt Device Group dgroup1i2 MF 54 REQUESTER lt 2 22 2 S lt 383 ots a on ee Se rq2 gt Requester white_4 requester2_1 unlocked Node white connected Spec requester2 Outlets outlet1 Active Request Alternative composite_rq1 100 status threshold rql gt Requester black_5 requester_1 unlocked Node black connected Spec requester Outlets outlet1 Active Request Alternative composite_rq1 1
315. sical with electrical considerations relevant to implementing a compliant device This is extended with engineering considerations as they relate to enabling proper electrical function to facilitate communication to or from a device Building on signaling basics is operation of the interconnect with consideration of interoperability between multiple devices and a bridge between interconnects From control of data transfers through to arbitrating access to the interconnect this level incorporates dimensions of timing concerns and recovery when signaling errors occur PCI revision 2 3 PCI SIG 2002 The USB interconnect also adopts a decomposition of the physical interface into electrical and mechanical specifications At the electrical level this includes transmission of a clock signal alongside data and similar attention paid to timing concerns Mechanically cables and a range of connectors are precisely drawn and engineering tolerances detailed USB 2 0 Compaq Hewlett Packard et al 2000 The Firewire interconnect likewise presents precise mechanical details for cables and connectors plus alternatives for differing use scenarios It also outlines timing for data signaling across the interconnect and dictates the requirements to implement a clock to facilitate synchronous operation Firewire400 IEEE 1995b Firewire400 IEEE 2000 Power requirements Interconnect specifications stipulate power requirements to be implemented by complian
316. sing existing applications which run unmodified Their focus is on the centralisation and coordination of the sharing process to combine resources that are available on nearby systems Resources are common system components expressed as services with well defined behaviours and control mechanisms clipboard storage file system display and USB interconnect based keyboards and mice The implementation referred to as the Composition Framework represents a thin middleware layer providing distributed transparency Defining Arbitrary Types for Devices A representative example of arbitrary typing is contained in the Digital Living Network Alliance DLNA standards for delivering media interoperability throughout a home Allegro Software 2006 Digital Living Network Alliance 2013 DLNA is used for music sharing and distributing digital video and is based on Universal Plug and Play UPnP UPnP 2008b The fundamental device model for UPnP consists of Devices Services and Control Points Devices are network entities providing one or more services which are basic units of control provide actions and have status via variables Control Points are network entities that are capable of discovering and controlling other devices The basic device model is extended through the UPnP AV specification UPnP 2008a This allows DLNA devices to interact with each other to pass digital content Interoperability guidelines define three categories Hom
317. sion of identity permits their consideration during composition This extends requests beyond concern for logical control where factors can be included that are form related aspects of a device and outside of logical interfaces The utility in our proposal is added flexibility to formulate requests in a completely different way to previous efforts Making properties part of the expression of type changes what is capable of being requested No longer is composition a matter of matching codes to identify devices Rather sought after functionality can be explicitly described and backed with properties related to form such as elements of the user interface 75 4 2 Exploring Structural Description To overcome the restrictions inherent in the use of named types we intend to change the way in which devices are identified Our proposed course of action is to formulate a device description at a finer granularity than a whole at the level of elements of discrete functionality The description built out of device elements is to be used in composition Its utility will be to provide a more flexible process of satisfying requests It is intended to be more than a substitute mechanism for arranging logical access Rather the ability to articulate non functional properties and explore describing logical control is about providing flexibility to how a request is formulated Device description is to be realised using a minimal abstraction of hardware The
318. sley Reading MA USA ISBN 0 201 06196 1 Lenorovitz D R Phillips M D Ardrey R S amp Kloster G V 1984 A Taxonomic Approach to Characterizing Human Computer Interaction In G Salvendy ed Human Computer Interaction Elsevier Science New York NY USA ISBN 0444423958 Leslie I M McAuley D Black R Roscoe T Barham P Evers D Fairbairns R amp Hyden E 1996 The design and implementation of an operating system to support distributed multimedia applications IEEE Journal on Selected Areas In Communications vol 14 7 DOI 10 1109 49 536480 pp 1280 1297 M Audio 2006 M Audio Audiophile USB Owner s Manual M Audio AP 050103 viewed March 2014 lt http www m audio com images global manuals Audiophile USB_Manual pdf gt Matrox Graphics Inc 1999 Matrox MGA G400 Specification datasheet 10617 MS 0101 Matrox Meijer E amp Szyperski C 2002 Overcoming Independent Extensibility Challenges Communications of the ACM vol 45 10 DOI 10 1145 570907 570929 pp 41 44 Mendes J M Leitao P Colombo A W amp Restivo F 2008 High Level Petri Nets control modules for service oriented devices A case study In 34th Annual Conference of Industrial Electronics ECON Merillon F Reveillere L Consel C Marlet R amp Muller G 2000 Devil An IDL for Hardware Programming Proceedings of the 4th conference on Symposium on Operating System Design amp Impleme
319. ss It presents a breakdown of forms of control be they polling queueing asymmetric and symmetric interrupts messaging and i o control blocks Smotherman 2000 This work presents a narrow perspective on categorisation to cast historical system architectures in terms of their handling of i o sub systems A CPU I O Interaction i synchronous transfer il asynchronous transfer a interlocked instruction to start transfer synchronisation by interlock synchronisation by polling separate instructions to poll and transfer data controller transfers words of blocks DMA controller with scatter gather capability I O channel with specialised I O instruction set I O processor synchronisation by interrupt separate instructions to transfer data controller transfers words of blocks DMA controller with scatter gather capability I O channel with specialised I O instruction set I O processor b conditional instruction to start transfer synchronisation by polling or interrupt c mailbox deposit to start transfer single entry synchronisation by polling or interrupt d queue insert to start transfer multiple entries synchronisation by polling or interrupt e asynchronous instruction to start transfer synchronisation by polling or interrupt B Multiprocessor I O i asymmetric initiation synchronisation by polling asymmetric interrupt symmetric interrupt ii symmetric initiation synchronisation by pollin
320. ss a distributed system they are discussed from the perspective of a particular computer system It is however worth pointing out that we could adopt the perspective of any one of the systems in the distributed system In which case the event sequences would end up being framed slightly differently 3 6 1 Device Connect A device connect event sequence covers preparing a device for participation in composition by configuring it for operation and recording its availability It happens as the IO_Discovery service enumerates devices attached to a computer system when powered on It also occurs when a device connects to an interconnect where the system is attached and subsequently assigned responsibility for the new device The event sequence outlined in figure 3 6 begins with IO Discovery passing notification to IO_Configuration to ready the device for operation local remote figure 3 6 device connect notes solid lines indicate sequences which occur whereas broken lines may happen depending on circumstances shaded area indicates where notifications are being exchanged on the same computer system 64 Part of this task is to setup resource availability with IO_Resources If the device or rather its driver code acts as a requester of further devices then IO Outlets is advised to setup records for tracking request satisfaction A positive change in resources triggers the match process by notifying IO Composition on the appoi
321. st of multiple DGroups iv where a search of a sub structure in a structural description fails to match try a further sub structure since there may be repeats of a taxonomic term at the same level When to cease backtracking During the search pursuit of particular solutions becomes pointless and it is inefficient to continue These consist of circumstances where a solution which has failed to satisfy is the only plausible result and any further options would make no sense Therefore it was necessary to build further heuristics into the process to inhibit backtracking Searches are constrained through use of the cut operator in Prolog in the following ways a when trying to satisfy the current request prohibit investigation extending back to requests already tried b when trying to satisfy the current RQGroup prohibit investigation extending to those already tried c where correspondence for a DGroup s structural description fails to reach the requester determined acceptance measure reject it without pursuing further ways of deriving that correspondence d where a sub match within a structural description fails to reach a requester s measure of acceptance or there is no match at all force rejection of the branch term amp any sub match without considering any further alternatives e once quantitative correspondence is determined at the leaf level within a structural description prohibit any further attempt to derive v
322. stem has a particular domain of useable devices irrespective of the effort required to integrate them into the system Achieving any degree of automation within the home demonstrates the inherent complexity to distributed systems The programming of control units illustrates the difficulties in making sense of other devices or even being made aware of the context of use This foreshadows potential problems with bringing additional control units into the house and having them be used or have additional devices be integrated into the suite of audiovisual equipment e g bringing another mobile phone into the house and having it be able to control anything or additional audiovisual component and ensure it may be operated once plugged into the system There is no treatment of how future devices are to be handled e g future audiovisual equipment being controlled by the existing system 1 3 The Challenge The scenario is relevant to our work because the distributed system automating the context of a home will need to endure possibly for more than 30 years During this time human users will frequently come and go with devices They can also be expected to arrive with new devices Furthermore device input output is a focus and remote control of them is a feature An objective of the system design is to automate tasks The actual example represents a bespoke solution and requires manual setup Alternate examples have adopted a similar approach as hav
323. structures This means using the same type dictionary and expressing them as a structural description 4 5 1 What Makes Sense to Request In formulating a request responsibility rests with the requester to provide sufficient detail The objective is to find acceptable correspondence Checking involves traversing a structural description used to represent a request and determining whether terms exist with a device We adopt the viewpoint of a requester and express device functionality from an external perspective A structural description utilises the taxonomy from which hierarchically related terms are drawn It is not necessary to articulate all details describing a device just those relevant to an adequate description and for control purposes As such it is permitted to repeat a term at the same level to provide a means of expressing additional options for the same element In the example shown below the modules articulated are those that are relevant to a request seeking an audio device capable of converting a digital stereo audio signal to analog Ina similar manner to devices structural descriptions for requests are expressed in the Prolog language as a list of lists task_element l task 11 1 1 01 01 011 l function direction uq us enum digital_to_analog sampling_rate frequency hertz 48000 data_channels system integer 2 bit_resolu
324. sulating a device Where variance occurs is that it may be to a whole device or just partial functionality The sort of entity to which access is granted may be represented by an object reference service interface remote procedure call a set of files or even user interface controls The first example is the participants in a Jini system which are all object oriented and based on Java They are of a particular class and utilise method invocations for communication Following composition matched services have proxy objects for them distributed to where the client is located This enables the client to use an object reference to make local method calls whilst being unaware of communication between proxy and the remote device service Newmarch 2006 A different access form is DLNA which begins with obtaining a UPnP service description via composition This includes a list of commands and parameters for each plus a list of data variables for the service The description in a XML template is retrieved using a web reference contained in the messages exchanged A requester control point invokes an action from the device s service via a form of remote procedure call As long as discovery advertisements from a device have not expired a control point may assume that the device and its services are available for access Allegro Software 2006 The Desk Area Network DAN project provides a further access example in the multimedia area Within
325. t ActiveCompRQ AMF loop to cancel each request from the existing match getRequesterSpec Requester Spec compositeRequest Spec ActiveCompRQ RQList cancelExistingRQMatch Requester Outlet ActiveCompRQ RQList 131 cancelExistingRQMatch _ _ _ cancelExistingRQMatch Requester Outlet ActiveCompositeRQ RQH RQT loop to cancel each group match with Requester amp Device getRequesterSpec Requester Spec request Spec RQH RQGroupList cancelExistingRQGroup Requester Outlet ActiveCompositeRQ RQH RQGroupList cancelExistingRQMatch Requester Outlet ActiveCompositeRQ RQT cancelExistingRQGroup _ _ _ _ cancelExistingRQGroup Requester Outlet ActiveCompositeRQ RQ RQGH RQGT matchTransaction Match Requester Out Let ActiveCompositeRQ RQ RQGH Device DGroup GMF _ Match remove application of match result with Requester amp Device applyMatchWithDevice remove Match applyMatchWithRequester remove Match then delete the match result from the database retract matchTransaction Match cancelExistingRQGroup Requester Outlet ActiveCompositeRQ RQ RQGT 5 3 2 Satisfying a Request Alternative Guidance on satisfying a request alternative impacts the requests contained in a list associated with them It ensures that satisfaction means every request is sufficiently matched How did it come about Without lists of requests or the ability to separate out a request it is possible f
326. t Shostak et al 1982 For device departure a check of a stored records is made to determine if that system was responsible Otherwise another computer system may have left requiring a further check to determine if the departing device was recorded as a gateway for communication with that system The resolution pathways for enumeration are summarised in figure 3 1 48 check device already assigned r gt for assigned flag system connects none device check system records exclusive lg device connects arrival for interconnect status shared success it interconnect probe interconnect amp signal gt check system records generated to determine status inter system negotiation for device assignment fail _ ignore device removal single check system records for device as gateway to other system other _ check system records for assigned status self g device disconnects figure 3 1 interconnect signaling resolution gateway g system disconnects When a device joins or departs this service must adjust its records and concludes by notifying the IO _ Configuration service to configure or remove the device Whereas when another system is arriving or leaving the consequences of more than a single system coming or going must be resolved This involves modifying records kept concerning the other systems in a cluster Enumerate the devices attached to a computer system Account
327. t devices These amount to whether power can be supplied from the interconnect or sourced back from the device Included are particulars of budgeting supply across multiple devices and managing a device transitioning from lower to higher consumption Across a range of interconnects they lack consistency to their use of terminology Furthermore a differing assortment of factors define power management for each specification It is left to driver code to determine correct settings to ensure a system continues to be viable In the case of Firewire IEEE 1995b IEEE 2000 devices nodes may be engineered as a power source power sink or neither and importantly may change roles as required The method by which its power class is indicated to others is via packet transmission or embedded in interconnect accessible data structures The specification stipulates that when implemented over cable the interconnect may be unpowered or powered from more than one power source Those devices providing power must meet particular requirements including over voltage and short circuit protection Where others detect cable power at the connector nominal range 8 30 volts they are required to make this indication logically visible via device based state Devices using cable power must also meet requirements related to sinking current up to 1 5amps and maximum consumption of power 3watts refer to section 8 3 cable power amp ground IEEE 2000 79 For USB
328. t or outlet defined as a logical structure that is configured to provide access to the interfaces of other software This is arranged as follows outlet requester outlet1 composite_rql _ composite_rq2 _ composite_rq3 _ inactive composite_rql a device with 4 channels composite_rq2 2 devices with 2 channels composite_rq3 4 devices with a single channel compositeRequest requester composite_rqi rq1 compositeRequest requester composite_rq2 rq2 rq2 compositeRequest requester composite_rq3 rq3 rq3 rq3 rq3 rql 4 channels together rq2 2 channels together rq3 single channel request requester rq1 rqg_channelui rqg_channelei rqg_channelui rqg_channelei rqg_channelui rqg_channelei rqg_channelui rqg_channelei request requester rq2 rqg_channelui rqg_channelei rqg_channelui rqg_channelei request requester rq3 rqg_channelui rqg_channelei ser interface controls for a channel lectrical interface connectors requestGroup requester rqg_channelui proximity _ u requestGroup requester rqg_channelei proximity _ e The example above seeking audio control surfaces illustrates how to layout multiple combinations that will be tried The ideal is expressed as the first composite request of a single device that has at least 4 channels of user interface controls for signal input with corresponding electrical interfaces Further alternatives co
329. t formulation for a given framing of how to derive satisfaction Describing a device is the means by which access is granted The process of composition draws upon a device description containing links to driver code to indicate the extent of access in the results Our assumption is that a requester in knowing how to describe a device in sufficient detail will also be aware of how to successfully control a device Fine grained structuring of requests and exploration of alternatives in the implementation has validated this as sound 6 2 Impact of Our Contribution The impact of our contribution on the home automation setting is outlined and more broadly on significant stakeholders 6 2 1 Achieving Context Awareness Within the home automation setting the impact of achieving context awareness is felt by control units having the capacity to dynamically discover devices in a room or as they enter a space More broadly distributed systems experience improved accounting for devices in the environment by continuously updating record of and initiating actions to deal with them The effect on stakeholders begins with users being provided with a more rewarding interaction via control interfaces reflecting the devices that are actually there When preparing requests inclusion of code for introspection of the context is no longer required Requests need only present a device description to be assigned control System administrators become less invo
330. task Initially we drew upon interconnect bridges as a guide to the sort of functionality that could be implemented by a task element module A bridge is effectively a mapping from one communication link to another This points to reliance upon the modules a task element connects to for assistance with describing functionality be they a communications link or an electrical interface This simplifies expression by suggesting the tasks being modeled are transformative taking a particular input performing a function and sending the result to the output Describing a range of functions is straightforward and can accomplished according to specified roles We are assisted in determining roles by devices being decomposable back to modules that are themselves based on an underlying physical implementation Patterns emerge that capture functionality encountered in the range of devices examined They are described below a formal role assigned and defined functionality requirements specified and an example provided to illustrate e adjust a digital or analog signal specify the characteristics of the electrical interface or the digital function e g digital or analog audio volume adjustment e convert signals from analog to digital ADC or from digital to analog DAC specify the DAC ADC conversion e g DAC codec converting PCM digital stream to analog audio signal e transform between communication links CL outline mapping between links e g from S P
331. tched value uq us enum required SC term approach SC term control gt checking availability of Registration Unit analog_audio_stream_in available A term direction matched value uq us enum analog_to_digital A term sampling_rate matched value frequency hertz 48000 A term data_channels matched value system integer 2 M C M C 176 A term bit_resolution matched value system bit 16 accept submatch match factor check 9 gt 9 M C SC term function A term principal matched value uq us enum convert M C SC term role M C SC term task accept submatch match factor check 14 gt 14 M C SC term task_element A term direction matched value uq us enum unidirectional A term logical_channels matched value system integer 2 A term model matched value uq us enum stream ccept submatch match factor check 4 gt 4 SC term link SC term primitives A term direction matched value uq us enum unidirectional A term logical_channels matched value system integer 2 A term model matched value uq us enum stream accept submatch match factor check 4 gt 4 M C SC term Link M C SC term primitives A term direction matched value uq us enum unidirectional A term logical_channels matched value system integer 2 A term signal_format matched value uq us enum digital A term model matched value uq us enum stream accept submatch mat
332. tems employing the Unibus interconnect Although utilising the connection slot to determine locality it relied upon device switches to determine which memory address region that particular device type s registers were to be mapped refer to discussion of setting addresses for memory mapping i o Varga 2010 The historical trend to performing conflict resolution in software principally by platform configuration code has not removed the dependency It simply targets resolving platform level reliability concerns With the gradual expansion of interconnect types and possible target devices from which to load the operating system a different set of issues has arisen for platform configuration The execution environment prior to loading an operating system is not intended to incorporate functionality akin to that once an operating system kernel takes control Its objective is to enumerate attached devices perform a conflict free allocation of system resources and configure sufficient devices to permit loading the operating system However the handling of devices is far from thorough and is restricted to those for which it has a driver The flow on effect is to reduce operating system awareness of devices to the contents of the tree structure handed over by platform configuration code which may not contain all attached devices due to interconnect types not being recognised Furthermore the operating system is unable to rely upon any firmware driver co
333. terconnect utilises copper in preference to the originally choice of optical fibre so that it can provide for a device to source power max 10watts Hachman 2011 Properties related to the physical The headings distilled from the discussion begin with physical manifestation of a device This combined with mechanical structures provide sufficient coverage to permit manufacture at the same time as offering a brief overview of dimensions and weight A distinct element is electrical interfaces which describe signal input output to from a device This means specifying the connector to ensure independently developed cables can attach to particular ports through to signaling details such as whether analog or digital to guide making connections with the external world Additional form related features are power management and timing matters Expressed as a range of terms charactering physical properties they break down as i physical manifestation dimensions e g length 100mm breadth 50m height 45mm weight e g 456grams ii electrical interface characteristics impedance dynamic range signal endedness data format iii mechanical structure cabling e g true connector e g mini stereo socket signal lines e g 3 direction e g output iv power management sink consumption rate supply consumption rate states e g always on v timing power on e g gt 7s clock generator rate states sink 84 4 2 4 Operation
334. term signal_mute maps gt state analog_audio_in_mute new value system boolean true amp retained value uq us Loff state update term bit_resolution maps gt state adc_resolution new value system bit 16 amp retained value system bit 16 state update term data_channels maps gt state adc_channels new value system integer 2 amp retained value system integer 2 state update term sampling_rate maps gt state adc_sample_rate new value frequency hertz 48000 amp retained value frequency kilohertz 44 1 completed applying RQGroup match to Device to constrain resource availability next RQGroup rqgroup2 gt gt gt gt gt gt gt try another DGroup dgroup1i1 from Device blue_3 audiophile_1 FHALETEAL HHHH HHHH FEET EEE ET EEE EEE ET EEE ET HE ETE TEETH EP Et ttt gt checking availability of Registration Unit analog_audio_stream_out available A term direction matched value uq us enum digital_to_analog A term sampling_rate matched value frequency hertz 48000 A term data_channels matched value system integer 2 A term bit_resolution matched value system bit 16 accept submatch match factor check 9 gt 9 M C SC term function A term principal matched value uq us enum convert M C SC term role M C SC term task accept submatch match factor check 14 gt 14 M C SC term task_element A term signal_ended matched value uq us enum unbal
335. the DAN the operating system is responsible for access control and protection This is to ensure that trusted components configure devices as nodes for communication The classes of device range from dumb supervised to smart They are delineated by the complexity of control interface and the extent of processing power associated with them Where a device node has no processing capability a software manager running on a separate processing node exports a remote procedure call like interface to clients refer to section on camera node device Barham Hayter et al 1994 Contrast is provided by the Plan 9 operating system which treats all resources including devices as files A requester uses a service connection server accessed through a file interface to establish distributed connections from a computer system The kernel maintains a database of mapping between symbolic system names and network addresses Presotto and Winterbottom 1993 This enables the namespace to be extended by grafting on remote file trees for access to i o resources Remote data communication or control happens by reading and writing to the data or control file associated with a device 39 Lastly both the iRoom interactive spaces implementation Ponnekanti Lee et al 2001 and the SpeakEasy approach at XeroxPARC Edwards Newman et al 2002 provide infrastructure support for generating user interfaces for control of devices The wrap up to composition invol
336. the distributed system Determining whether change has occurred on a particular computer system is linked to the support services which are discussed in the next section The trigger for conduct is a positive change in device resources on any system resulting in the IO_Composition service being notified to perform matching Reference is made to a record of the appointed match system and notification sent to IO Composition on that system to begin Where this is the same system the process simply commences On the assigned system this service begins by distributing notification that requires a check for unsatisfied requests This involves a multicast to members of the cluster using a record maintained by IO Discovery As services on other systems determine that requests are insufficiently satisfied they are submitted back to match system and queued The process is only invoked when there are resources available As such it proceeds all the way through to matching when at least one unsatisfied request is submitted A further notification is sent requiring a check for available devices As systems determine resources are available devices are submitted back to the match system to form a 60 pool The process selects the request at the front of the queue and proceeds to find a solution which satisfies the constraints from amongst the pool Application of results wrap up The outcome will be a request is unable to find satisfaction or else a matc
337. those specifically related to the process of configuration This means examining the dependencies devices and their driver code have upon other elements are indicated in figure 2 1 driver code i o device kernel code dependencies platform configuration code upon interconnect specification processor kernel code driver code platform configuration code dependencies upon interconnect specification processor figure 2 1 device and driver code dependencies upon system elements Each of these relations is elaborated upon with details of the context in which the dependency arises Where device type is referred to this is an indication of the sort of functionality implemented by the device This is different from device identity which is a device based structure that provides a means of denoting device type reporting locality and providing a unique identifier Also reference to device description is defined as a device based structure that denotes its type It is used by our work to contain structures defined in subsequent chapters The complement to device description is a request which is a logical structure expressed using the same building blocks as a device description 1 Device Dependency Upon Driver Code The most fundamental dependency is that between a device and driver code For driver code to prepare hardware for operation it must have an awareness that extends beyond any
338. tion system bit 16 role 01 011 principal uq us enum convert control 1 0 1 approach 1 11 operate ug us enum required communications_link 1 primitives 1 link 1 1 1 direction uq us enum unidirectional logical_channels system integer 2 signal_format ug us enum digital model ug us enum stream channel 1 compression ug us enum uncompressed data_format ug us enum pcm_audio 111 111 Placeholders for a set of annotations empty square brackets pertain to the requester These refer to seeking access to driver code interfaces being configured for access and a series of enhancements relevant to composition They are discussed in detail in the next chapter 105 Sectioning expression of Requests At this point a request is generated as a single structural description in terms of modules Because devices are expressed at a finer granularity than a whole similar adjustment is necessary when requesting modules To accord with devices and be able to check for correspondence the same structure is required We establish boundaries around elements that are significant to a request aligning them according to functionality signal paths or exterior elements spatial co loca
339. tion To finalise the definition of a ROGroup we associate structural descriptions with them and have a request consist of a list as follows rqgroup1 rqgroup2 rqgroup1 taskflow rqgroup2 taskflow request requester rql requestGroup requester requestGroup requester se be The example below is a request for a device capable of audio streaming in and out The same request is contained in the worked example included in the appendices The facts listed illustrate how we accomplish building a request by using RQGroups to structure association The modules TE EI CL UT divide into the following RQGroups 1 TE ADC CL DigitalIn TE Mute EI AudioIn 2 TE DAC EI AudioOut CL DigitalOut request requester rq1 rqgroup1 rqgroup2 requestGroup requester rqgroup1 taskflow _ task_element 1 task 1 1 function 1 direction sampling_rate data_channels bit_resolution role 1 1 1 principal 1 rl 1 Lcommunications_link primitives ee task_element task function data_forma signal_mute role 1 principal compression data_format l 1 0 1 0 t U Ti U ll 1 0 electrical_interface characteristics electrical signal_ended dat
340. tion between human user and computer Classifying interfaces in Virtual Environments The concern of Virtual Environments VE is real time interactive graphics with three dimensional models when combined with a display technology that gives the user immersion in the model world and direct manipulation Fuchs and Bishop 1992 4 Existing VE systems employ a strictly limited set of devices comprising displays enhanced by artifacts embodying auditory and haptic modalities Some have suggested that problems inherent in VE systems stem from an inadequate interface to the capacity of human senses Collectively they explore the possibilities for future devices Aukstakalnis and Blatner 1992 Kalawsky 1993 Ellis 1994 Their discussion of potentials is important because it focusses around understanding interaction through the human perceptual system rather than actual devices Significantly Ellis describes input and output channels through human interface requirements by taking the human sensorium as a structuring element The resultant breakdown of the communication between human user and simulation hardware is indicated in figure 4 4 Ellis 1994 19 This serves to quantify interaction providing a useful set of properties relevant to the devices employed in computer systems studied It also serves however to underline the perception that VEs principally rely upon visual display devices complemented with additional means of interaction
341. tion is possible using structural descriptions it was not explored in our implementation and remains a promising research angle to pursue Accomplishing automatic control Although a device can describe required control and introspection of a structural description is possible this does not accomplish automatic configuration of logical control We adopt a different approach to solving this by suggesting that a logical consequence of a requester having the capacity to describe module functionality is being able to pinpoint the control required The low level device abstraction used in the taxonomy makes this possible A device specifies where driver code interfaces link to modules in a structural description This is accomplished by annotating a structural description at the relevant point and necessarily relies upon driver code interfaces being tailored to accord with a device description Requesters follow up by describing the modules they are capable of controlling and placing annotations at points where they are capable of providing control These link to code interface templates which describe how they intend to logically control a module The implication is that requesters can only gain access to driver code interfaces by describing a device then indicating where they expect control points to correspond How this works when implemented is discussed in the next chapter in the section under process enhancements Further use of annotations to fu
342. tion table includes details of how processor independent i o access gets expressed in native instructions This record is static but specific to the processor for a computer system 3 3 7 Changes to Computer System Specifications Define a processing module as the core of a computer system A trend when specifying interconnects has been to allow for dynamic device connections To account for this we propose a processing module as a way of refining the concept of a platform specification and to incorporate our concept of dynamic assignment of responsibility for devices Computer systems represent a fundamental building block for the distributed system and are the entities to which devices become associated Architecturally a system describes where generalised processing capability is located It must be of sufficient capability to permit distributed services and driver code to execute in a cooperative multitasking manner In organisational terms a computer system comprises a processing module to which devices connect A minimal definition of a processing module consist of one or more general purpose processors and associated main memory The processors are connected across an interconnect to a specially tasked bridging device and a variety of devices are attached to an interconnect on the other side A typical computer system is indicated in figure 3 5 with a processing module at its core and a tiered layout for interconnects processor main m
343. tions means the entity controlling a computer system must handle these events It is also in recent initiatives addressing security of system memory using device related memory management units that we find dependent relations emerging The handling of device configuration as a result of dynamic connection events involves allocating system resources In this case we are focussing on the operating system being responsible It remains a matter of maintaining system viability by avoiding conflicts with the allocation of logical resources be they memory regions or interrupt signaling The complexity inherent in accomplishing this task has seen research focus on 22 improving the logic of configuration and not merely the mechanisms Schupbach Baumann et al 2011 Furthermore the kernel must have an awareness of the interconnect type to which the device has just connected This means an operational interconnect bridge driver for detecting the event and permitting minimal device access In a similar manner to device dependency upon platform configuration code the kernel performing conflict resolution targets system level reliability concerns but in no way removes the dependency For performance reasons devices have evolved to being granted direct access to system memory for use as an input output buffer In the context of an operating system employing virtual memory the kernel is responsible for managing the virtual to physical translation of acc
344. to address issues with semantics in a number of ways Firstly an enhanced capacity for description is achievable through our focus on the broadest domain of devices A unified vocabulary arises out of collating those properties revealed and defining them independently Level of detail The level of detail concerns classification at a level of granularity which may be of use over and above the purposes of a taxonomy In setting out to address shortcomings present in the use of named types our proposal for a structural approach to device description deals with concerns over the level of detail Devices composed of elements establish the granularity of reference and the framework gains structure by properties being attributed to elements Conceptual basis The presence of a conceptual model concerns its articulation and its underpinnings being identifiable in the development of a taxonomy Devices composed of elements which are described by properties form the basis of our conceptual model Beyond the architecture of existing computer systems we have articulated properties inclusive of those relevant to interconnects the user interface and capturing a full spectrum of device form and function Measurability This means considering measurable descriptors e g communications channels in contrast to absolute factors e g device types for a taxonomy and permitting equivalence of 94 quantitative measurements between taxonomies Our efforts addr
345. to logical parameters in the computer 77 Linear Rotary X Y Z rX rY 1Z 5 Selection gt 5 P o SSS b Q R 3 ON f Station _ O Volume S g dP ies R EF L Mouse oS 4 S F T 2 H D 4 ZS aF age Ow 5 1 10 100 1 10 100 10 100 1 10 100 1 10 100 1 10 100 Measure Measure Measure Measure Measure Measure figure 4 2 Card s Input Device Taxonomy Circles are used in the diagram to indicate that a device senses one of the physical properties shown on the vertical axis along one of the linear or rotary dimensions shown on the horizontal axis For example the circle representing the radio volume control indicates a device that senses an angle around the Z axis The position in a column indicates the number of values that are sensed the measure of the domain set Another example is the circle representing the selection control represents a discrete device Lines are used to connect the circles of composite devices A black line represents a merge composition such as the X and Y components of a mouse The dashed line represents a layout composition such as the three buttons on a mouse represented by a circle with a 3 in it to indicate identical devices Card MacKinlay et al 1991 106 Card et al do not separate devices from consideration of the man machine interaction Their research extends previous taxonomic efforts and has the capacity to account for a greater ra
346. tocol is required to dictate how driver code is to be initialised and instructed to perform device configuration This is to happen after the driver code block has been extracted from a device description and translated to native code for the processor We shift driver code bootstrapping away from being defined by contemporary operating system development environments Instead an independent definition structures them and provides an outline of the configuration process This is required in the first instance to develop driver code Then the IO Configuration service with an awareness of code structure and the protocol for initialisation attends to automatically controlling a driver to perform device configuration and ready itself to control device operation 3 3 6 Records Maintained Translation table for virtual processor to native code static The IO_Configuration service extracts driver code from a device description This block is compiled to an intermediate byte code format based on a virtual processor Architecturally this means an instruction set that is defined for use as a target when compiling higher level languages To complete removal of the dependency driver code has upon the processor this involves supplying details of the native processor to perform code translation We accomplish such by reference to a persistent resource consisting of a table detailing virtual 56 processor to native instruction set translation The transla
347. tream_out available A term direction matched value uq us enum digital_to_analog A term sampling_rate matched value frequency hertz 44100 A term data_channels matched value system integer 2 162 A term bit_resolution matched value system bit 16 accept submatch match factor check 9 gt 9 M C SC term function A term principal matched value uq us enum convert M C SC term role M C SC term task accept submatch match factor check 14 gt 14 M C SC term task_element A term signal_ended matched value uq us enum unbalanced A term data_format matched value uq us enum analog A term connection_establish matched value uq us enum hot_pluggable accept submatch match factor check 4 gt 2 M C SC term electrical M C SC term characteristics A term width matched value length mm 8 3 M C SC term physical_dimensions M C SC term physical_manifestation A term connector matched value uq us enum rca_connector rca_connector A term direction matched value ug us enum Loutput A term classification matched value uq us enum external accept submatch match factor check 8 gt 7 M C SC term structures M C SC term mechanical_structure A term device_boundary matched value system boolean true M C SC term relation M C SC term lLogical_structure accept submatch match factor check 14 gt 9 M C SC term electrical_interface HEHHEHE HHHH HHHH HHHH HHH
348. trol A term direction matched value ugus enum unidirectional 1 A term logical_channels matched value systen integer A term signal_format matched value uq us enum fotettatit A term model matched value ug us enum stream accept submatch match factor check 6 gt 4 M C SC term link term compression matched value uq us enum unconpressed A term data_format matched value uq us enum pem_oudio accept submatch match factor check 6 gt M C SC term channel M C SC term primitives accert submatch match factor check 12 gt 9 MESE t comm nications Amk ies eii term principal matched value uq us enum adjust M C SC term Pole me i M C SC term task A term principal matched value uq us enum adjust M C SC term role M C SC term task A term principal matched value uq us enum adjust M C SC term role M C SC term jp gGhecking availability of Registration Unit analog audio_stream_out Ate nfigure matched value ug us enum required M c SC term approach M C SC term control A term data format matched value ug us enum digital A term signal_mute matched value system boolean true M C SC term function A term principal matched value uq us enum adjust M C SC term role M C SC term task A term configure matched value uq us enum required A term operate matched value uq u3 enum required SC term approach SC term FFK
349. trol required of device elements This leads into describing significant elements that implement functionality As part of accounting for interconnect bridges we begin refine the expression of functionality into roles The granularity to task expression emerges as significant in capturing their decomposition Further properties related to configuring a device fall under logical resource requirements and are expressed at a finer granularity Then representing device state is acknowledged as a property that can be used in the expression of other categories This emerges as a theme we shall return to when compiling the taxonomy Expressed as a series of terms charactering these properties they break down as i control approach e g ordering command sets configuration or operation commands e g state change link source temporality response i task elements role e g adjust convert transform evaluate translate bridge director function e g digital to analog sampling rate data channels bit resolution iii logical requirements system resource e g interrupt or reserved memory region 4 2 5 Concurrency and Sharing Access The sort of access concurrency possible and arbitrating that access to a device are important considerations when seeking to satisfy a request Capturing both in device descriptions would permit factoring them into composition This allows requesters to seek exclusive access or have access resolved t
350. ts Western Digital Technologies 2010a Properties related to non functional aspects The properties distilled from factors outside of logical control demonstrate a similarity between performance guarantees and estimates of fault free operation These qualities describe specific device elements related to functionality or to those manifesting in the physical environment namely the user interface and connectors Expressed as a series of terms charactering these properties they break down as e fault tolerance logical detection scope fault approach timeframe reporting scope fault notification avenue guarantees scope specifics distinction quantity 4 2 7 Finer Grained Description Decomposition of a whole device into elements introduces the need to account for its structure This includes description logical connections and dataflow between elements Including these in device description would allow a request to seek a particular data or signal format for an input output of key device elements It would also provide the ability for devices to present an informative picture of themselves at a logical level A rich description of elements could be built out of traversing logical connections We provide an illustration of existing efforts at providing logical descriptions of devices Then we discuss accounting for structure as they are decomposed into elements which leads into characterising communication between elements Self de
351. ts support service is to participate in the automatic establishment of device access by managing external access points belonging to requesters By external access points or outlets we mean a logical structure used by services to provide details of where to contact a device in a distributed system They are associated with a request that describes the sought after device IO Outlets also receives notifications to establish the records for a requester or remove them As the process of composition commences it performs checks to determine if any requesters on a computer system have 62 outlets that insufficiently satisfied In response this service submits request structures associated with an outlet An initial table of outlets is established when a requester arrives on a system and is updated as match results are applied or removed IO Outlets is consulted as a way of checking systems for any unsatisfied requests 3 5 4 IO Results The JO _ Results support service manages the results across the distributed system Once composition concludes and results are received by a system this service becomes the coordinator for their application It notifies IO Resources and IO Outlets services to ensure the result is applied or cancelled with a particular requester or device Match results may be applied separately and remotely from where the process was conducted As such the collective record of results represents all resource allocation to or f
352. ture IEEE Standards Organisation New York NY USA ISBN 0 7381 2941 0 Intel Corporation Inc 1999 Preboot Execution Environment PXE Specification v2 1 Intel Corporation Denver CO USA Intel Corporation Inc 2002 Extensible Firmware Interface EFI Specification v1 10 Intel Denver CO USA Intel Corporation Inc 2002 Enhanced Host Controller Interface Specification for Universal Serial Bus Standard rev 1 0 Intel Corporation Inc 2005 Intel 975X PCI Express Chipset datasheet 310158 001 Intel Intel Corporation Inc 2006 Intel PCI Express I O Controller Hub 7 ICH7 Family datasheet 307013 002 Intel Intel Corporation Inc 2008 Intel Virtualization Technology for Directed I O Architecture Specification specification rev 1 2 Intel Intel Corporation Inc amp Microsoft Corporation 1994 Plug and Play ISA Specification ver 1 0a Intel Denver CO USA Internet Engineering Task Force 1999 Simple Service Discovery Protocol Operating Without an Arbiter specification v1 00 IETF Isaac M 2011 Google s Platform Extends Its Reach With Android Home Wired viewed March 2014 lt http www wired com gadgetlab 2011 05 android at home google io gt Johanson B Fox A amp Winograd T 2002 The Interactive Workspaces Project Experiences with Ubiquitous Computing Rooms JEEE Pervasive Computing DOI 10 1109 MPRV 2002 1012339 pp 67 74 Johnson J Roberts T L Verplan
353. ty This work contains no material which has been accepted for the award of any other degree or diploma in any university or other tertiary institution to Nicole Kaiyan and to the best of my knowledge and belief contains no material previously published or written by another person except where due reference has been made in the text I give consent to this copy of my thesis when deposited in the University Library being made available for loan and photocopying subject to the provisions of the Copyright Act 1968 I also give permission for the digital version of my thesis to be made available on the web via the University s digital research repository the Library catalogue and also through web search engines unless permission has been granted by the University to restrict access for a period of time Nicole Kaiyan 2014 vii viii Contents Abstract Acknowledgements Statement of Originality List of Figures 1 Introduction 1 1 Home Automation 1 2 Analysing the Example 1 3 The Challenge 2 Issues with Distributed Systems 2 1 Building a Capacity to Endure 2 1 1 Model of the Process 2 2 Discovery 2 2 1 Achieving Remote Awareness 2 2 2 Shortcomings in Distributed Awareness 2 3 Configuration 2 3 1 Articulating System Dependencies 2 3 2 Impact of Dependencies 2 4 Composition 2 4 1 Describing Devices 2 4 2 Problems With Device Descriptions 2 4 3 The Distributed Match Process 2 4 4 Issues With Distributed Composition 2 5
354. ty from amongst the broadest pool of devices 146 Appendices Appendix A Audio Device Description Collectively the devices presented below are used for recording and playback of audio attached to a computer system They comprise functionality for analog to digital and digital to analog audio conversion with those more capable including a MIDI IN OUT interface and digital audio IN OUT A cross comparison of key features is presented after the devices are described and diagrammed A 1 1 Griffin iMic v2 The Griffin iMic v2 device implements a simple set of audio related functionality which contributes to a manageable logical description It is classified as an analog to digital audio convertor used for recording and playback of mono or stereo audio from a computer Griffin Technology 2010 It manifests as a processing box with a cable for attachment to the USB interconnect of a computer system as indicated in figure A 1 Stereo Out Stereo In Mic Line Level Switch figure A 1 Griffin iMic v2 line drawing Externally the box has Audio IN and OUT ports to which attach the source and destination respectively for analog audio Additionally there is a toggle switch for adjusting MIC LINE level of the audio IN port Device Description The product brochure for a Griffin iMic v2 contains insufficient detail to provide the granularity to description sought Hence this requires augmenting with details of a chip from a devic
355. ual rel 0 4 LIRISA Reveillere L amp Muller G 2001 Improving Driver Robustness an Evaluation of the Devil Approach In Proceedings of the 2001 International Conference on Dependable Systems and Networks DSN 01 Goteborg Sweden pp 131 140 Ryzhyk L Chubb P Kuz I Sueur E L amp Heiser G 2009 Automatic Device Driver Synthesis with Termite In Proceedings of the 22nd ACM Symposium on Operating System Principles SOSP Big Sky MT USA DOI 10 1145 1629575 1629583 pp 73 86 Saha D amp Mukherjee A 2003 Pervasive Computing A Paradigm for the 21st Century IEEE Computer vol 36 3 DOI 10 1109 MC 2003 1185214 pp 25 31 Satyanarayanan M 2001 Pervasive Computing Vision and Challenges JEEE Personal Communications vol 8 4 pp 10 17 Savant Systems 2011 SmartSystems home automation platform Savant viewed March 2014 lt http www savantsystems com new_savant_products aspx gt Schattkowsky T amp Muller W 2004 Vodel Based Design of Embedded Systems In Proceedings of the 7th IEEE International Symposium on Object Oriented Real Time Distributed Computing ISORC pp 121 128 Schupbach A Baumann A Roscoe T amp Peter S 2012 A Declarative Language Approach to Device Configuration ACM Transactions on Computer Systems TOCS vol 30 1 DOI 10 1145 2110356 2110361 191 Shanley T amp Anderson D 1995 PCI System Architecture PC System Architectu
356. uester the annotations returned in the results link to a table which is a fact for managing access to external code interfaces outletCodeInterfaceList requester adjust_adc_settings Reference to device code interfaces is also via annotations at the branch level for example they appear as facts associated with the task_element module te4 inside the 3rd square bracket deviceElements imic2_dgroup3_te4 ladc_configure As the results are applied device annotations refer to code interface headers used to populate the requester s table of external code interfaces codeInterface imic2 adc_configure set_sample_rate set_resolution set_channels Once the table is populated with matched code interfaces they are asserted as facts codeInterfaceTable requester outlet1 composite_rqil rql rqgroup1 adjust_adc_settings imic2 dgroup3 adc_configure set_sample_rate set_resolution set_channels Note the list of code interfaces last entry in brackets above is purely a placeholder and could be expanded as required for any programming environment 121 Goal expression The application of match results occurs where an alternative has been satisfied There are a series of goals that are used to traverse the result list and apply the match A significant sub goal applyMatchWithRequester processes annotations related to code interfaces as follows applyMatchWithRequester Mode Match Requester Out L
357. uiring teardown and the boxed area represents services on remote systems Removal commences by advising IO Results to cancel all match results involving the requester With reference to stored results they are reversed on that system For each IO_Outlets tears down record of the match Notification is also passed to other systems that need to cancel with the other participant They utilise their IO Results service to perform match reversals The task concludes by removing all record of the requester Where at least one result was reversed the process is triggered and IO Composition notified on the appointed system requester local ae cancel_all_matches _cancel_all_mafches_ involving equester remote cancel_all_ matches_ from_requester requester_remove cancel_match_from_requester r el remote remote cancel_ all matches_ from_requester pe multicast cancel_match_frgm_requester ae p r match 7 figure 3 11 requester cancel notes solid lines indicate sequences which occur whereas broken lines may happen depending on circumstances 3 6 7 Perform Match A perform match event is about conducting composition across a distributed system It is divided into a preparatory and wrap up stage The preamble determines participants and submits them to the appointed system Then the process seeks to satisfy a request from amongst a pool of devices Following this a wrap up involves results being sent ba
358. unctionality Task analysis research in HCI has accounted for device function from an information processing system perspective In covering input processing then output tasks it is descriptive and by breaking down complex tasks it manages to subdivide functionality Our concern in building a framework to describe functionality is that it adequately characterises the whole of a device then for it to be decomposable into elements In his work on a Task Strategies Approach Miller developed and refined a systems task vocabulary Fleishman Quaintance et al 1984 He set out to realise a transactional definition of tasks by starting with a conceptual model that assumes humans are analogous to an information processing system The resultant task functions were defined in great detail for practical use by analysts They are presented in figure 4 8 along with a brief description to aid interpretation Fleishman Quaintance et al 1984 287 EST figure 4 8 Miller s Systems Task Vocabulary 86 The tasks 25 in total appear under the subheadings of i input mode message source 11 processing rules operations for translating input into output and iii output condition operational result Others have deemed the Task Strategies Approach applicable to computer systems design with the task functions being regarded as describing human and machine behaviour Fleishman Quaintance et al 1984 Lenorovitz Phillips et al 1984 F
359. up dgroup3 from Device red_1 imic2_1 adding match for RQGroup rqgroup3 to match list for Request rq4 apply match with Device red_1 imic2_1 MODE apply Request Group rqgroup3 Device Group dgroup3 registration units audio_stream_in updated gt unavailable state update term bit_resolution maps gt state adc_resolution new value system bit 16 amp retained value system bit 16 state update term data_channels maps gt state adc_channels new value system integer 2 amp retained value system integer 2 state update term sampling_rate maps gt state adc_sample_rate new value frequency hertz amp retained value frequency kilohertz 44 1 completed applying RQGroup match to Device to constrain resource availability gt completed matching entire RQGroup list for Request rq4 172 X checking have derived a match for Request rq4 adding match for Request rq4 to match list for Request Alternative composite_rq3 next Request rq5 with RQGroup list rqgroup4 gt gt gt gt gt try another Device red_1 imic2_1 next RQGroup rqgroup4 gt gt gt gt gt gt gt try another DGroup dgroup1 from Device red_1 imic2_1 FHL ETEAT ETE HHHH HHHH HHHH EEE EE ETE EE ETE EEE TEE EE EP ETE EEE FHF ETEET ETE ETHEL EEE ET HEEL EE EET EET EEE HHHH checking have an acceptable RQGroup match comparing match factors is gt 23 gt gt gt gt gt gt gt try another DGroup d
360. us enum rca_connectorrca_connector A term classification matched value uq us enum external A term device boundary matched value syst m boolean true M C SC term relation M C SC term logical_structure A term width matched value Clength mm 8 37 M C SC term physical dimensions M C SC term physical_manifestation A term connector matched value uq us enum rca_connector rca_connector A term classification matched value ug us enun external J A term device_boundary matched value syst m bodlean true M C SC term relation M C SC term Logical_structure A term connector matched value uq us enum rca_connector rca_connector A term classification matched value ug us enum external A term device boundary matched value syst m bodlean true M C SC term relation M C SC term logical_structure A term signal_ nded matched value ug us enum unbalanced A term data_format matched value uq us enum analog A term connection establish matched value ug us enum hot_pLuggable accept submatch match factor check 4 gt 2 M C SC term electrical C SC term characteristics A term classification matched value A term Classification matched value faus zenun external FHAPETEET ETE EE HHHH H HHHHHHHHHH HHH HHHH checking have an acceptable RQGroup match comparing match factors is 26 gt 42 ERROR no match found for RQGroup rqgroup1 with Device
361. uses the request to fail to reach a Requester stipulated acceptable level e failure to find acceptable matches at a higher priority leads to trying lesser priority requests e during the process application of a match to Device happens for 1st DGroup then reversal upon failure to match 2nd DGroup from same Device e lowest priority request alternative Composite Request satisfies leading to a partial match being recorded for Outlet outletl Active Request Alternative Request Alternative List composite_rq1 100 composite_rq2 75 composite_rq3 50 composite_rq4 25 composite_rq5 20 gt gt gt try another Request Alternative composite_rql at priority 100 with Request list rq1 next Request rq1 with RQGroup list rqgroup1 rqgroup2 gt gt gt gt gt try another Device green_2 us224_1 next RQGroup rqgroup1 gt gt gt gt gt gt gt try another DGroup dgroup21 from Device green_2 us224_1 FHEHELEPELE PETE PETE ETE tt ttt ttt ttt tt tttttttttttttt ttt ttt FHEPETEEL HHHH HHHH EEE ET EEE ET EEE ETE ETE EE ETE ETE TEETH EET ttt checking have an acceptable RQGroup match comparing match factors is gt 42 gt gt gt gt gt gt gt try another DGroup dgroup22 from Device green_2 us224_1 FHEHELEHELE HTTP ETE tt ttt ttt ttt ttt ttttttttt ttt ttt gt checking availability of Registration Unit analog_audio_stream_in available A term direction matched value ua us enun Lonalog to digit
362. uter systems Additionally how the process is conducted is a matter of accounting for new devices and satisfying requests that arrive The complexity to the search is also related to the what is being matched The first example of HomeOS from Microsoft Research opts for user mediated management of composition Dixon Mahajan et al 2012 This happens when a new application or device is added to a centralised datastore HomeStore for the home network It is used to host all applications and drivers and indexes application manifests devices and exported services 37 When installing an application HomeOS walks the user through setting up access This task involves specifying which devices an application should be allowed to access Reference is made to a manifest that an application provides describing required services Since the number of devices may be large only compatible matched device services are shown The user selects which services the application can access Adding a new device involves the user specifying its location and configuring which applications should be granted access This is simplified by only presenting applications that are compatible match with the new device An example expanding the where is DLNA It delivers media interoperability across a home network making use of UPnP to define composition Microsoft 2000 UPnP 2008b Devices send out messages advertising themselves their services and the location o
363. utlet CompRQ RQ RQGroup ODInterface ATerm AV retract dataInterfaceTable Requester Outlet CompRQ RQ RQGroup ODInterface ATerm AV 123 5 2 4 Quantitative Correspondence Motivation Separation of the quantitative from the qualitative of the i o taxonomy is a design choice we made to provide structural descriptions with greater potential to persist without need for continual adjustments and additions To improve the capacity for the taxonomy to persist qualitative terms are derived from the taxonomy from branch through to leaf level however the values assigned at the leaf level are defined separately The quantitative is served by standardising the units through adopting an existing system of measurement The SI system provides base units plus those derived including units with special names and symbols and a category for units outside SI Thompson and Taylor 2008 The physicality of devices and their interface to the physical world justifies choosing a straightforward way to qualify leaf terms It avoids the problem of having to arrive at an arbitrary set of measures and link them to our taxonomy Instead SI provides classifying units of measurement quantities and enables ready conversion within classifications symbols It also permits evaluating the overlap when matching similar values both range and value s The potential exists to extend the set of standard units without any taxonomic impact Providing basic data types
364. value uq us enum analog A term connection establish matched value ug us enum hot_pluggable accept submatch match factor check 3 gt 2 M C SC term electrical M C SC term characteristics A term classification matched value fug us enum external A term Classification matched value ug us enum external HEHHEHE HHHH HHHH FEET EEE ET EEE ETE ET EEE ET EE TEEPE TEEPE t ttt checking have an acceptable RQGroup match comparing match factors is 26 gt 42 ERROR no match found for RQGroup rqgroup1 with Device red_1 imic2_1 reversing application of group matches so far with same device aborting Request List at rq2 amp returning null match 171 X checking have derived a match for Request rq2 ERROR no match found for Request rq2 reversing application of matches for prior requests with respective device s aborting Request Alternative composite_rq2 amp returning null match X checking have derived a match for Request Alternative composite_rq2 gt gt gt try another Request Alternative composite_rq3 at priority 50 with Request list rq4 rq5 next Request rq4 with RQGroup list rqgroup3 gt gt gt gt gt try another Device red_1 imic2_1 next RQGroup rqgroup3 gt gt gt gt gt gt gt try another DGroup dgroup1 from Device red_1 imic2_1 HEHHEHE HHHH HHHH HHHH HHHH EEE ETE ETE TEETH ETE TEE TEEPE TEE Et FHEPETEEL ETE EE HHHH EEE ET EEE ETE PTET PETE EE ETE ETE EEE TEEPE ttt Et c
365. ve composite_rq1 gt completed matching entire Request List for Request Alternative composite_rq1l X checking have derived a match for Request Alternative composite_rql MATCH RESULT match found found match for Request Alternative at priority exceeding 50 for Outlet with pre existing match cancelling existing match for Request Alternative composite_rq3 involving RQList rq4 rq5 cancelling existing match for Request rq4 involving Request Group List rqgroup3 cancelling existing match for Request Group rqgroup3 involving Device Group dgroup3 from Device red_1 imic2_1 match factor 26 apply match with Device red_1 imic2_1 MODE remove Request Group rqgroup3 Device Group dgroup3 registration units audio_stream_in updated gt available state update term bit_resoLlution maps gt state adc_resolution value system bit 16 with no retained state found state update term data_channels maps gt state adc_channels value system integer 2 with no retained state found state update term sampling_rate maps gt state adc_sample_rate value frequency hertz 48000 with no retained state found apply match with Requester black_5 requester_1 MODE remove code adjust_adc_settings Request rq4 Request Group rqgroup3 gt DeviceCodeInterface adc_configure set_sample_rate set_resolution set_channels data audio_in_settings Request rq4 Request Group rqgroup3 bit_resolution system bit
366. vel recognition of departure or arrival This means applications based on these notifications can rely on them being carried up the protocol stack and discovery being triggered Bluetooth SIG 2009 What discovery needs is linkage between low level hardware events and the rest of the process configuration amp composition This means deciding on which events generated on a computer system are relevant to devices and determining what to do when they happen Then what notifications to send to other systems and how to respond to such when received from the wider distributed system 11 Failure to reach distributed agreement Despite the relative uniformity of expressing device functionality as services and the use of multicasting on IEEE802 interconnects interoperability eludes existing work The diversity to abstraction which is covered in the next section is a factor as is a slightly different framing of the process For interoperability to be a reality there needs to be distributed agreement on what is being discovered be that a service resource device or a code interface However the challenge continues to be seen as purely a practical obstacle of arriving at the same vocabulary and syntax Kindberg and Fox 2002 This fails to consider the semantics of the process which would lead to determining what notifications to send between distributed system 12 2 3 Configuration Significance to a distributed system A separate stage
367. ves sending this interface for a specific device service to the requesting appliance It is the human user that is granted access to the device through the controls provided in the user interface 2 4 4 Issues With Distributed Composition Spanning the when where and how of the process plus access establishment there are patterns to the key issues raised by distributing composition These are summarised below Further failure to reach distributed agreement Interoperability between different distributed systems eludes existing work Our earlier observation of a failure to find agreement on the semantics of discovery extends to composition This begins with differing mechanisms for initiating the process It continues with the protocols used to define how matching proceeds across a distributed system There is an inconsistent treatment of computer system events leading to a wide disparity in the distributed notifications used in existing systems Lastly incompatible structures mean the exchange of data relevant to matching is not possible Even the sharing of terms to describe a device presents a problem Lack of automation to the process Distributed composition is not treated as a process to be managed entirely by system software Although cooperation does occur at particular stages such as matching of terms the distributed process is not conducted automatically There is an explicit need for participants to intervene to initiate steps or
368. ving the device With 65 reference to stored results each is reversed on the computer system This involves IO_Resources being advised to remove record of resource allocation If the device acted as a requester then IO Outlets tears down record of the match Notification is also passed to other systems that need to cancel with the other participant in a match These systems utilise their IO Results service to perform match reversals The task concludes by removing all record of the device Where the device acted as a requester and had a result cancelled the process is triggered by notifying IO Composition on the appointed system 3 6 3 System Connect A system connect event involves one or more computer systems attaching to an existing cluster of systems It occurs when a device connects to an interconnect where a system is attached and its IO_Discovery service determines that the device has already been assigned to another system The event sequence outlined in figure 3 8 covers the composition related aspects of resolving a system connecting to a cluster It begins with IO Discovery passing notification to IO Resources The computer system indicated by the shaded area is the one where a system connect is raised and the boxed area represents services on remote systems The task begins by IO_ Resources checking resource availability and notification is passed to other systems to do likewise They utilise their IO Resources service to perfor
369. x Timer Handling kernel timerc figure 2 6 overview of DDE Linux2 6 environment for L4 kernel provides general Linux kernel interface emulation for Linux device drivers under L4 implemented as a set of interfaces to particular subsystems refer to Linux Device Driver Environment Manual v0 5 2 4 27 Helmuth 2003 Despite drivers being separately deployable software units kernel dictates contribute additional complexity and bulk in terms of structure and the manner of communication These considerations are over and above device specific or even interconnect related code Drivers based upon Windows Driver Model WDM for Microsoft s XP Vista 7 operating system necessitate developers being aware of support code requirements and then to include blocks of kernel code to enable execution Oney 2003 The contingent nature of these dependencies means they apply to only that kernel This is despite driver code having similar logical resource requirements irrespective of which kernel such as requiring memory allocation or access to a memory region Attempts to address these issues have resulted in tailored development environments for the preparation of drivers These environments endeavour to tackle complexity by defining a series of device types based 20 around those encountered on system platforms for which the operating system is targeted In the case of Apple s I O Kit there is little support offered for device types outside th
370. y happen depending on circumstances 67 Handling of this event involves cooperating IO_ Discovery services adjusting records kept on the cluster of systems Because more than one system may have disconnected this involves shrinking an existing cluster and may involve appointing a different system to be match Resolving issues related to the dynamics of clusters relies upon empirical investigation and has been left to a future implementation Hence we assume they have been resolved prior to the sequence indicated It is also possible to have multiple gateways to other systems by virtue of more than one interconnect being shared by bridging devices from the same systems A determination is made of when a gateway to a system has been removed However issues related to determining alternate routes of communication is beyond the scope of our work 3 6 5 Requester Create A requester create event sequence covers establishing those aspects of a requester related to composition and readying them for participation in the process The event occurs when a requester is deployed to a particular system and notification is passed through to the IO_Requesters support service The event sequence outlined in figure 3 10 covers tasks relevant to composition As such it begins with notification that a requester has been deployed and needs to be established on the system This is accomplished by advising IO Outlets to establish external access point records cont
371. y to satisfy requests for devices not yet developed Our goal is to build a distributed system with the capacity to endure along with the home for the next 30 or more years Making progress towards improving the ability to utilise devices and lessen the brittleness to system configuration would remove the need for a bespoke approach Additional control units could then be added to a context and future devices be incorporated into the home There is the potential to make a longer lasting contribution by attacking a broader problem In an environment where multiple devices are integrated into artifacts they are dealt with by fixing the system configuration at the time of engineering Enhancing our ability to deal with devices as they are discovered would enable access to that functionality across separate engineering worlds This would be noteworthy in permitting distributed systems of devices to be constructed dynamically and reconfigured into the future 2 Issues with Distributed Systems In this chapter the technical requirements are established for building a distributed system We introduce a model of the process for gaining access to devices and use this to examine existing work in distributed systems The issues raised at each stage form a framework within which a series of design requirements are derived 2 1 Building a Capacity to Endure Our analysis of the scenario of automating a home brought up the challenge of devising more flexible way
372. ying goal supplied by that participant These goals perform a minimal set of checking operations conducted in a secure manner since the parameters supplied are limited to the sub match and those from the participant e g state A match condition is expressed in Prolog code and consists of e verifying a term is present in the sub match e verifying quantitative correspondence at the leaf level in the match results amp e comparing participant state against quantitative correspondence in the match results Implementation specifics The implementation links to match conditions in either participant through annotations at the branch level for example appearing with task_element module 1st square bracket in a structural description task_element te3 mc1 dac_configure task analog_audio_stream_out function 0 1 The annotation mc is used as a reference to a goal that is supplied by the participant When tried it performs a check before acceptance of a sub match into the results matchCondition D _ SubMatch mc1 state D active_units ActiveChannels service_SubmatchValue DataWidth primitives channel data_width SubMatch service_SubmatchValue DataRate primitives channel data_rate SubMatch cut audioSetting ActiveChannels DataWidth DataRate device constraints on channel allocation audioSetting _ _ _ 0 _ _ _ 16 _ _ _
373. ynchronous Transmit Response Block figure 2 4 range of Firewire packet formats for asynchronous data transmission 16 destinationOffsetHigh amp destinationOffsetLow refer to a devices address space destinationID refers to the bus and node number identifying a device IEEE 19956 152 In addition to the means of access a specification dictates the format of a range of logical structures visible from the interconnect and stipulates means of accessing those remaining on the device This extends to stating the approach that must be taken to enumerate structures and utilised in current systems to provide an indication of resources required by a device Firewire defines an interconnect visible structure referred to as a bus information block As detailed in figure 2 5 this guides identification and is supplemented by reference to a more comprehensive block indicating capabilities t Q 31 h 1 33h 3 39h 9 34h 4 BUS_ID 8 bits 8 bits 8 bits 8 bits 1s D wi i SS ESSER B cycck acc m amp gen BUS_OPTIONS E SSSEEShS amp bis shts AO pnd 3 ts F O Q node_vendor_id chip_id_hi GLOBAL_UNIQUE_ID_HI 24 bits 8 bits oO 7 chip_id_lo GLOBAL_UNIQUE_ID_LO 32 bits figure 2 5 format of Firewire bus info block starts at location FFFF F000 0404 in a device s address space node_vendor_id chip_id_hi amp chip_lo combined represent unique EUI 64 identity c

Intelligent discovery, configuration and composition of devices in a

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