Minimalist and Intuitive User Interface Design Guidelines for
Contents
1. J OURNAL OF OB ECT TECHNOLOGY Online at http www jot fm Published by ETH Zurich Chair of Software Engineering JOT 2007 Vol 6 No 3 March April 2007 Minimalist and Intuitive User Interface Design Guidelines for Consumer Electronics Devices Seonghoon Kang and Won Kim Samsung Electronics and SungKyunKwan University Suwon S Korea Abstract People today come in contact with many consumer electronics CE devices in their daily lives CE devices have become increasingly complex with added functionality devices from different vendors provide different user interfaces for the same functionality similar devices from the same vendor provide different user interfaces for common functionality As a result usability of CE devices has become a serious challenge for most users In this paper we put forth design guidelines for making user interfaces for CE devices easy to understand for most everyday users To do this we first present a taxonomy of user interface dimensions for CE devices We then present our design guidelines against core elements of the taxonomy and apply them against various popular CE devices The designing guidelines when applied consistently and diligently can help bring some order to the current state of user interfaces for CE devices The results of this paper should be applicable to a good extent to general digital systems Keywords User Interface Ul Human Computer Interface HCI Usability CE d2. 49 MINIMALIST AND INTUITIVE USER INTERFACE DESIGN GUIDELINES FOR CONSUMER ELECTRONICS DEVICES would not mean much to a large segment of everyday users Such technical term as 70Mbytes should be translated to a term that would be both relevant and easily comprehensible to the ordinary users such as x number of additional songs may be recorded x minutes of additional video may be recorded etc Mismatch of the PUI and NPUI elements violation of consistency and minimum Figure 4 shows volume control interfaces of an MP3 music player The up and down movement of the touch pad on the player PUI and the circular GUI feedback display NPUI do not match The inconsistency between the two UI elements burdens the users with one extra UI element and paradigm to deal with Volume up Volume down Volume up Volume down PUI Operation SUI feedback Figure 4 Inconsistent volume control interfaces PUI and NPUD Use of different words symbols and labels for the same functions within the same devices or across different devices violation of consistency 99 66 The selection button is labeled variously as select confirm or OK on different devices Similarly the power on off button comes with different symbols on different devices as shown in Figure 5 l l I O DTV O lap Cell Phone Figure 5 Examples of the use of different symbols for the same function Inconsistent operat
3. Conference on Information Visualization London August 27 29 1997 VOL 6 NO 3 JOURNAL OF OBJECT TECHNOLOGY IMALIST AND INTUITIVE USER INTERFACE DESIGN GUIDELINES FOR CONSUMER ELECTRONICS DEVICES Barr P Biddle R Noble J A Taxonomy of User Interface Metaphors Tech Rep CS TR 02 11 School of Mathematical and Computing Sciences Victoria University of Wellington New Zealand 2002 8 Kang S and Kim W Taxonomy of CE User Interface In Proceeding of the Next Generation PC 2006 Conference Ilsan Korea Nov 2006 available only in Korean About the authors Won Kim Professor and Univeristy Fellow with the School of Information and Communication Engineering at Sungkyunkwan University Suwon S Korea He is Editor in Chief of ACM Transactions on Internet Technology www acm org toit He is nd _ Global General Chair of the Human Society Internet International Conference He is the recipient of the ACM 2001 Distinguished Services Award and is an ACM Fellow He can be reached at wonkim skku edu Seonghoon Kang is a researcher at Samsung Electronics Suwon Korea He received a Ph D in computer science from Korea University His research interests include user interface digital content management computer vision and pattern recognition He can be reached at shoon kang samsung com 52 JOURNAL OF OBJECT TECHNOLOGY VOL 6 NO 3
4. as a framework for understanding all dimensions of the UI and identifying more precisely where we should apply our design guidelines The taxonomy shown in Figure 1 consists of five parts corresponding to five dimensions of the UI for CE devices namely physical vs non We note that an earlier version of this taxonomy was the subject of a very short paper by us in Korean that we presented in a domestic Korean conference 8 We include an upgraded version here to provide a basis for presenting our design guidelines VOL 6 NO 3 JOURNAL OF OBJECT TECHNOLOGY 41 MINIMALIST AND INTUITIVE USER INTERFACE DESIGN GUIDELINES FOR CONSUMER ELECTRONICS DEVICES physical aesthetics and emotion convenience operation mechanisms information and information architecture When designing a user interface every dimension has to be accounted for 2 1 Physical vs Non Physical The first dimension is whether the user interface is physical or non physical PUI Physical User Interface e Physical user interface refers to the physical user interface elements on the CE device with which the users interact This includes physical buttons switches wheels knobs stylus touch screen keypad microphone monitor speaker digital camera video recorder etc on CE devices including remote controls NPUI Non Physical User Interface e Non physical user interface refers to logical user interface elements such as alphanumeric information
5. identify a user interface element 2 4 Operating Mechanisms The next dimension in user interface is the operating mechanisms for the devices Broadly this may be classified into those that are common to many types of devices and those that are specific to a given type of device The operating mechanisms apply to both the physical and non physical aspects of the user interface There are many mechanisms for operating devices physically such as moving a cursor pressing a button throwing a switch touching a touch screen typing on a keypad gesture motion etc Common operating mechanisms e power on off e menu operations open close 4 way navigation select release exit back e alphanumeric data input and manipulation of displayed alphanumeric data Device specific operating mechanisms TV channel up down display modes picture in picture mode etc digital still cameras zoom in out shot mode flash mode etc MP3 music players media play control play pause fast forward etc other devices tilting shaking touching Both types of mechanisms have a very important common sub mechanism namely error handling mechanisms Error handling mechanisms typically use visual or audio information Sometimes however they involve a device lockout There are two ways to handle error e Error prevention ignoring input requiring confirmation circulative menu navigation etc e Error warning issuing of a warning message and or s
6. many functions are crammed into many of the devices 3 The increasing number of functions leads to many types of information to store and display 4 There are many methods to represent the information 5 There are many modes of interaction with the users 6 There are many ways to appeal to the user s sense of aesthetics and emotions Beyond these the UI has not been a high priority item for the vendors as they have chosen to focus on the other more pressing items to survive in the market such as cost reduction pricing distribution marketing design hardware quality features and name branding Further as we will see shortly the UI have several dimensions in our view user interface designers have devoted time on those dimensions that appeal to the emotions of the users and devoted much less energy and thought on those dimensions that deal with how everyday users can comprehend the functions and information contents of the devices Some researchers proposed taxonomies of the UI and human computer interaction systems Chignell made an early attempt at a taxonomy of human computer interaction and standardizing terminology 5 Coomas and Timmermans proposed a taxonomy of physical media representational modalities and human computer dialogue semantics 6 Barr et al considered a principled understanding of user interface metaphors and provided a taxonomy for discussing and analyzing them 7 We developed our own taxonomy
7. non physical aspect of the UI of several representative CE products from leading vendors The discussions serve two purposes one is to illustrate each of the design guidelines in concrete contexts and another is to demonstrate the merit of applying the design guidelines in identifying the problems and fundamental reasons for the problems with the UI in today s CE devices To protect the commercial interests of the vendors we shall not name them 48 JOURNAL OF OBJECT TECHNOLOGY VOL 6 NO 3 Nested menu structure violation of minimum It has long been established that the depth of a menu hierarchy should be limited to 3 or under We have found for example that the external connection setting function on some digital TV menus is 4 level deep as shown in Figure 3 Either the top or the second level of the menu hierarchy may be eliminated to fix this problem Channel External connection External Input 1 VCR DVD STB External Input 2 VCR DVD STB Component Input 1 VCR DVD STB Level 1 Level 2 Level 3 Level 4 Figure 3 The menu structure for the external input connection setting function on a DTV Overlaying of functions violation of minimum and intuitiveness The menu button on some digital TV remote controls has three functions overlaid on it open close and back Only the open and close functions should be overlaid to make the button a toggle button that the ordinary users w
8. or images or video displayed on the monitor voice or sound heard via the speaker etc Such information is the result of a command the user issues an action e g turning the power on off the user takes or the occurrence of an abnormal condition Often there are many categories of such information and many of the categories may logically best be decomposed into sub categories As such the information has to be organized in a hierarchical structure known as information architecture Information architecture refers to the organization of such information 2 2 Aesthetics and Emotions The next dimension in user interface refers to user interface elements that appeal to the aesthetics and emotions of the users This dimension applies to both the physical and non physical aspects of the user interface This has five aspects corresponding to the five sensory functions of the human In practice though only three aspects are relevant Visual aspect color brightness contrast etc shape size arrangement of the PUI and NPUI user interface elements graphics images animation video symbols etc design and appearance of a device 42 JOURNAL OF OBJECT TECHNOLOGY VOL 6 NO 3 Physical a ii PUI NPUI Aesthetics and Emotions Visual aspect Auditory aspect Tactile aspect Convenience oO Ease of operation Ease of Element Identification Operating mechanisms o Common operating mechanisms Device specific operating mechani
9. sign near an exit ramp on the highway correspond to streets or other highways etc AKO P a high level mute stop don t right increase decrease low level Figure 2 Intuitive Symbols The meaning of each physical and non physical UI element on a CE device must be intuitively clear to everyday users Figure 2 shows some UI symbols whose meanings should be intuitively clear to everyday users The sequence and combination of UI elements too must be intuitively clear To design the UI for CE devices to be intuitively clear to everyday users the designers must exploit the common knowledge and acquired intuition of the users and must be very careful not to venture outside of the scope of such knowledge and intuition The ultimate goal of the UI for CE devices should be to make it possible for most everyday users to be able to use the CE devices without having to consult the user manuals The following further explains what it means for the UI to be intuitive e When it is necessary to overlay several functions on one button there should be relationships among the functions that are intuitively clear For example the left and right navigation functions are overlaid on the message box button on some cellular phones and the flash mode button on some digital still cameras This is not intuitive since there is no obvious relationship between the navigation function and the messaging function on cellular phones or between the navigation function
10. IST AND INTUITIVE USER INTERFACE DESIGN GUIDELINES FOR CONSUMER ELECTRONICS DEVICES 3 1 Minimum As the number and types of features keep increasing it is easy for UI designers to increase the number and types of UI elements The number and types of UI elements must be kept to a minimum Specifically the number of symbols icons labels font styles font sizes text colors background colors modalities the number of items and depth of the menu hierarchy etc should be kept to the minimum If some redundancy is to be built in it must be done in very careful consideration of the business requirements The following explains what it means to minimize various UI elements e The number of physical UI elements such as input buttons on a device should be minimized to correspond to the most frequently used functions Less frequently used functions should be manifested as non physical UI elements that is as items on a menu For example there should not be buttons on a television remote control for functions such as memorize or erase a channel the users should be directed to the menu to find items corresponding to such functions In this way UI designers should prevent the remote control from being crowded with buttons and labels for non frequently used functions e When it is necessary to overlay several functions on one button the number of overlaid functions should be limited to 2 The general public has been accustomed to toggle sw
11. and the flashing function on digital still cameras Even if the user is able to operate this function by first reading the manual the user is likely to have to consult the manual again after not using the functions for a while e The icons and symbols must be symbolic of the functions they represent For example on a 4 way navigation button there should be up down left right VOL 6 NO 3 JOURNAL OF OBJECT TECHNOLOGY 47 MINIMALIST AND INTUITIVE USER INTERFACE DESIGN GUIDELINES FOR CONSUMER ELECTRONICS DEVICES symbols and on a volume up down button there should be corresponding symbols such as e The symbols labels icons words phrases etc should be easily comprehensible to everyday users In other words such technical phrases as 700 Mbytes of storage remaining on a music player should be eliminated Appropriate color should be used for warnings and emphasis 3 3 Consistency Consistency cuts across all aspects of every UI element in every CE device Once a particular symbol is chosen for a particular function it should be applied consistently throughout the UI This should certainly be done within a particular device and preferably also across devices of different types that happen to share the same function We define inter device consistency to be consistency between different types or models of CE devices either from the same vendor or different vendors for example digital televisions and digital still camer
12. as We define intra device consistency to be consistency among UI elements on one particular type and model of device In general there should be inter device and intra device UI consistency Today as we will illustrate in the next section both inter consistency and intra consistency are inadequate As a result everyday users have to learn to operate each device separately because each device has a different menu structure different icons and symbols for the same or similar functions different words and symbols even on the same device etc As CE devices of the same type and even of different types share common functions the ultimate goal of consistency should be unification i e standardization of the UI elements for these common functions The following explains further what it means for the UI elements to be consistent e The menu layout and the navigation and selection of menu items should be consistent e The selection of the font style font size colors etc should be consistent e The selection of icons symbols and labels should be consistent for the same or similar functions For example if a left arrow is used for left navigation on the menu of a digital television it should be used not only on all left navigations on the menu but also on the remote control and even on the music players from the same vendor 4 APPLYING THE DESIGN GUIDELINES TO CE DEVICES In this section we apply the three design guidelines to the
13. ctronics LG Electronics TiVO and Apple Computers By analyzing the UI of these devices we arrived at a minimum set of design guidelines Although we are not at liberty to divulge our findings with respect to Samsung Electronics products suffice it to say here that we have reported our findings and recommendations to the top management for action and the top management has accepted most of our recommendations 40 JOURNAL OF OBJECT TECHNOLOGY VOL 6 NO 3 The contribution of our research is the minimum practical set of guidelines for designing the UI of CE devices to substantially help everyday users to comprehend the functionality and information contents of the devices We believe the set of guidelines can apply to a large extent to general digital systems and should also be useful to technical users The remainder of this paper is organized as follows In Section 2 we present a taxonomy of user interface dimensions for CE devices In Section 3 we discuss a minimum practical set of design guidelines for CE devices In Section 4 we make the design guidelines concrete and illustrate the effectiveness of our guidelines by identifying how each of them is violated in CE devices Section 5 concludes the paper 2 A TAXONOMY OF USER INTERFACE DIMENSIONS Before proceeding let us see the reasons for the current sad state of the UI for CE devices 1 There are many types and many models for each type of CE devices 2 Increasingly
14. e CE devices have become rather complex as vendors have added new features and functions in order to differentiate from competitors and also to justify raising the price CE devices of different types have some frequently used common functions such as power on off channel up down date time setting etc however different vendors offer very different UIs for these functions Even worse vendors of the same family of CE devices offer different UIs for the devices Further the UIs are often inconsistent and difficult or impossible to follow without consulting user manuals For those features that are not often used each time they are used the manuals need to be consulted The UI may not be the most important factor that determines the commercial success of CE devices For example the commercial success of digital televisions is determined by the picture quality price design functionality and the brand name However once parity is established on these factors UI becomes a key differentiator among competing products Today due to competitive pressures in the market parity has been established on most of the important factors and UI remains a factor that can help vendors differentiate from others As CE devices are used by everyday users not just engineers or artists their UIs must be designed for ease use and comprehension by everyday users Various researchers have suggested guidelines for designing a UI Shneiderman and Plaisant sugges
15. erstand appear on the menu or even the devices Further icons are often not symbolic of the corresponding functions and only their designers can appreciate their meanings The users need to consult the user manuals to be able to operate the devices or navigate the menu However to 46 JOURNAL OF OBJECT TECHNOLOGY VOL 6 NO 3 compound the matter the manuals too are often difficult to understand or may have long been misplaced People in reasonably industrialized parts of the world today are exposed to everyday UI elements in their daily lives These include a variety of doors home office hotel automobile combination locks public transportation systems automobile dashboards automobile and airplane seatbelts road signs traffic signals signs in public places elevators toasters washing machines hair dryers treadmills etc Beyond these many use some of the many CE devices personal computers and the World Wide Web Further many are exposed to UI elements in performing their jobs such as machine tools heavy industrial and farming equipment weapons airplanes trains ships etc As such everyday users may reasonably be expected to possess some common knowledge and experience based intuition about the meanings and basic ways to operate various UI elements This includes for example the fact that the red color or flashing light implies a warning the power button on a CE device is an on off toggle switch the lines on a road
16. evices 1 INTRODUCTION People today use many types of consumer electronics CE products including cellular phones music players DMB digital multimedia broadcast players personal digital assistants digital televisions video recorders digital cameras smart refrigerators video security systems automobile navigators digital clocks calculators etc besides personal computers laptops and computer based systems and equipment at home and work All the functions these devices and systems provide all the information they contain and all the responses they make to user commands are exposed through the user interface UI Ideally the UI should be designed so that most everyday users can without having to consult the user manual easily figure out how to use all of the primary functions of the devices and systems easily comprehend all of the basic information they contain and easily comprehend Cite this column as follows Seonghoon Kang and Won Kim Minimalist and Intuitive User Interface Design Guidelines for Consumer Electronics Devices in Journal of Object Technology vol 6 no 3 March April 2007 pp 39 52 http www jot fm issues issue_ 2007 03 column5 MINIMALIST AND INTUITIVE USER INTERFACE DESIGN GUIDELINES FOR CONSUMER ELECTRONICS DEVICES most of the responses from them Sadly however the state of UI for CE devices and many of the general digital systems today is well short of the ideal Many of th
17. ing mechanisms within a menu violation of consistency The back button on digital TVs or DVD recorders is used either to exit the current menu or to return to the upper level menu screen However in some devices it is used to exit all active menus Inconsistent operating mechanisms between similar devices violation of consistency The menu button on digital TVs is used for the menu open and menu back functions while the menu button on some of the DVD recorders is used for the menu open and menu close functions 50 JOURNAL OF OBJECT TECHNOLOGY VOL 6 NO 3 5 CONCLUSION As the number of types and models and the features and capabilities of consumer electronics CE devices have increased during the past decade usability of the devices has become a major challenge to everyday users Unfortunately the vendors have not satisfactorily addressed this challenge Although there have been a number of sensible guidelines for usability of digital systems in general they appear not to have had sufficient impact on the design of the UI for CE devices In this paper we started with the obvious notion that in order for the CE devices to be usable to everyday users the UI must be simple To be simple we believe that the UI must diligently and consistently adhere to three principles minimum intuitiveness and consistency To make the discussions of the three principles concrete we first described our ta
18. itches and for example it is reasonable to overlay the on and off functions on the power button However it causes confusion if 3 or more functions are overlaid on a button for example the open close back functions on a single menu button e The use of icons symbols and labels for both physical and non physical UI elements should be minimized In other words no icons symbols and labels should be used unless they are necessary Icons symbols and labels that make no sense to the users or are difficult or impossible for them to easily comprehend and remember are regarded as unnecessary and should be eliminated or modified e The number of font sizes font styles and colors used should be minimized Mixing more than a few font sizes font styles and colors in general distracts the users e Labels phrases and sentences on both the physical and non physical UI elements should be brief and clear e The number of items on a menu screen should be kept to fewer than 7 or 8 to avoid cluttering the screen e The depth of a menu hierarchy should be limited to 3 or fewer It is difficult to trace the menu structure and be aware of the nodes and paths followed if the depth is more than 3 3 2 Intuitiveness The labels symbols icons words phrases and sentences on many CE devices and on the menu are often difficult to comprehend intuitively Sometimes words phrases and sentences that only engineers can und
19. ould expect Either the back function should be removed from the remote control or should be placed on the menu or perhaps even overlaid with some other function on another button on the remote control Hidden functions violation of intuitiveness The program reservation function on some digital TV does not exist on the remote control and it is an item on the Program Guide menu screen This presumes that the users will browse through the programs and upon finding a desired program will reserve a desired program However the label Program Guide would convey to ordinary users the notion that the menu screen would only provide program information and does not convey the notion that the act of reserving programs would be a part of it To fix this problem either the label Program Guide should be changed to Program Guide and Reservation or a separate menu screen should be created for Program Reservation at the same level as Program Guide Use of difficult or non helpful words or phrases violation of intuitiveness Some digital TVs and DVD recorders are found to use technical terms or words and phrases whose meanings are not clear on the menu screens and help screens These include such words and phrases as display mode audio mode SRS internal amplifier v mode equalizer free space remaining 70Mbyets etc These VOL 6 NO 3 JOURNAL OF OBJECT TECHNOLOGY
20. ound blinking light etc 2 5 Information and Information Architecture The information and information architecture dimension refers to the information content and the organization of the information In our taxonomy this refers only to the non physical aspect of the user interface and does not include the aesthetics and emotions dimension There are two types of information in terms of whether it is to be input by the user or to be viewed and manipulated by the user The use of information may be for the installation and operation of a device or for viewing by the user as shown below Device facing information e installation initial setting values etc 44 JOURNAL OF OBJECT TECHNOLOGY VOL 6 NO 3 e operation input for menu navigation control and data input input for error handling etc User facing information e installation cable connection help information for initial setting including on line manual etc e operation operating mechanisms for the menus buttons switches etc e representation labels icons symbols buttons etc feedback on user input device status information error feedback etc The information may also be classified in terms of the types of data to be input or output as follows Device facing information e visual information image finger print pupil picture etc text title name description etc numeric channel setting values etc date and time system time reserva
21. sms Information and Information Architecture D Device facing information User facing information Figure 1 Taxonomy of CE User Interfaces Auditory aspect e tone loudness of sound intonation accent etc e sound effects bell sound animal sound etc Tactile aspect e texture weight elasticity of a device etc 2 3 Convenience The next dimension of the UI is convenience to the users This refers to ease of use and is certainly an important determinant of the usability of a device In particular there are two types of convenience One is ease of operating a device and applies to the physical aspect of the user interface Another is ease of identifying user interface elements and applies to both the physical and non physical aspects of the user interface Ease of Operation e shape size and layout of PUI elements e sound flashing or blinking light e other characteristics of a device that make it easier to see understand press grasp touch and feel a device etc Ease of Identification e shape size and color of PUI elements e font size font style font color and background color of text etc VOL 6 NO 3 JOURNAL OF OBJECT TECHNOLOGY 43 MINIMALIST AND INTUITIVE USER INTERFACE DESIGN GUIDELINES FOR CONSUMER ELECTRONICS DEVICES e shape size color and layout of NPUI elements etc e sound flashing or blinking light etc e other characteristics of PUI and NPUI elements that make it easier to
22. ted 8 golden rules 1 A good UI should have consistency provide universal usability provide meaningful feedback include an exit interface prevent errors make rollback easy be always controllable and reduce data which should be memorized to operate the device Ferr et al suggested 5 characteristics of determining usability 2 learnability efficiency repeatability error rate and satisfaction Norman suggested that basic principles of a good design for human are providing good a conceptual model and being visible 3 Smith and Mosier offer guidelines for designing the UI for software in six functional areas data entry data display sequence control user guidance data transmission and data protection 4 These are all valid guidelines However in our view they have not been well heeded by UI designers of CE devices on the market today as evidenced by the sad state of the UI As a result we have decided to see if we can help to bring some order into the UI of CE devices by proposing a minimum set of very practical design guidelines To do it we first developed a taxonomy of user interface dimensions in CE devices The taxonomy provides a framework for understanding more precisely how we apply our design guidelines For our research we analyzed MP3 music players digital TVs DVD recorders digital still cameras DMB players PMPs Personal Portable Multimedia Players and cellular phones The vendors included Samsung Ele
23. tion time scalar volume play position etc e audio information voice sound etc User facing information e visual information image icon image graphic animation video etc text menu label description message etc numeric channel setting values etc date and time system time reservation information program information etc scalar volume play position etc attributes color font size font style blinking etc e audio information voice melody sound effect etc e other modalities vibration haptic information 3 DESIGN GUIDELINES We now present our minimal set of guidelines for designing the user interface of CE devices with the view to making it as easy as possible for everyday users to comprehend all primary functions and primary information contents of CE devices The guidelines apply to all five dimensions in our taxonomy We start with a very simple premise that is the UI must be simple To be simple the types and number of UI elements must be minimal all UI elements and their combinations must be intuitively comprehensible to everyday users with minimal exposure to some CE devices and there must be consistency among all UI elements and their combinations Further the minimum and intuitiveness guidelines must be applied consistently throughout the UI design Below we examine each of these three guidelines for making the UI simple VOL 6 NO 3 JOURNAL OF OBJECT TECHNOLOGY 45 MINIMAL
24. xonomy of UI elements for CE devices and then applied the principles to various UI elements in a number of popular CE devices on the market We believe that the set of principles being minimal and intuitively obvious in themselves should be able to serve as very practical guidelines for the designers of UI and CE product development executives in the vendors ACKNOWLEDGEMENTS This research was supported in part by the Korean Ministry of Information and Communication under the ITRC Information Technology Research Center support program supervised by the IITA Institute of Information Technology Assessment IITA 2006 C1090 0603 0046 REFERENCES 1 Shneiderman B and Plaisant C Designing the User Interface Strategies for Effective Human Computer Interaction Addison Wesley Computing 2004 2 Ferr X et al Usability Basics for Software Developers IEEE Software 18 1 22 29 2001 3 Norman D A The Psychology of Everyday Things Basic Books 1988 4 Smith S L and Mosier J N Guidelines for Designing User Interface Software Tech Rep ESD TR 86 278 Hanscom Air force Base Mass USAF Electronic Systems Division NTIS No AD A177198 1996 5 Chignell M H A Taxonomy of User Interface Terminology In Proceedings of ACM SIGCHI 21 4 April 27 34 1990 6 Coomans M K D and Timmermans H J P Towards a Taxonomy of Virtual Reality User Interfaces In Proceedings of the International
Download Pdf Manuals
Related Search