Springer-Verlag NY User Guide
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1. 4 The rube Framework for Personalized 3 D Software Visualization The rube Framework The rube Framework s Precursor Object Oriented Physical Mul timodeling In previous research Cubert et al 5 Fishwick 6 and Lee and Fishwick 7 have worked on the development and implementation of an object oriented simulation application framework Object Oriented Physical Multimodeling OOPM is a system that is a milestone product of this previous research 5 7 OOPM extends object oriented program design through visualization and a defi nition of system modeling that clarifies and strengthens the relationship of model to program 3 The physical aspect of OOPM reflects a model design philosophy that recommends that models components and objects should be patterned after the structure and attributes of corporeal objects Within OOPM programs are multimodels 6 8 9 10 A multimodel is de fined as a hierarchically connected set of dynamic behavioral models where each model is of a specific type and the set of models may be homogeneous or heterogeneous 5 8 The basic dynamic behavioral model types are numerous and include Conceptual Model CM Finite State Machine FSM Functional Block Model FBM System Dynamics Model SDM Equation Constraint Model ECM Petri Net PNET Queuing Net QNET and others 8 OOPM supports the creation and execution of several of these model types including CM FSM FBM SDM ECM and RBM Th2. with out solid empirical results as a design guide We are still in the exploring and engineering phases of our research Although this chapter presents some pre liminary results of our effort in rube s development environment and modeling methodology more work is needed before we can reasonably proceed with hu man based empirical research We have very recently conducted a survey with general discussion of aesthetic methods within a class on Modeling and Com puter Simulation The results from this survey are not yet available at the time of this writing but will be made available in the near future In this chapter we have provided an overview of the rube framework as well as provided example worlds The emphasis for rube is to permit modelers greater freedom in building their own personalized software visualizations We briefly described a web based graphical GUI that allows to users to merge 3 D geometry an XML model file and pre existing behaviors for animating and simulating dynamic software models Possible benefits of the rube framework and future directions were discussed As software engineering further leverages modeling our research may help in the mainstream future definition of 3 D software visualization References 1 A F Blackwell Metaphor in Diagrams Ph D dissertation Darwin College Univ of Cambridge Cambridge UK 1998 2 C D Hundhausen S A Douglas and J T Stasko A Meta Study of Algorith
3. The rube Framework for Personalized 3 D Software Visualization John F Hopkins and Paul A Fishwick Department of Computer and Information Science University of Florida Gainesville FL USA 2 The rube Framework for Personalized 3 D Software Visualization Introduction Abstract In this chapter we discuss a software modeling and visualization framework called rubet This framework facilitates the creation of three dimensional 3 D software visualizations that integrate both static software architecture and dy namic real time operation A unique aspect of rube is that it does not tie devel opers down to a set of predefined symbols objects or metaphors in their visualizations Consequently users have the freedom to develop their own rep resentations The rube framework s general approach to software modeling and representation are discussed Next a simple example is developed according to rube s systematic modeling and visualization process Lastly benefits of the framework and future directions are discussed Background Modeling plays an important role in many computing tasks including software engineering and software visualization SV The first two phases of the model ing process involve system understanding and model representation In the cur rent context a system is any real world e g ecosystem or abstract e g database entity and a model represents the discrete objects and interactions between objects i
4. a com plex system with many components In this process there would be no more than one metaphor to map to each major model component in the following step i e step 4 However for the sake of discussion we choose two metaphors that will map to our single FSM and we will show the application of these two meta phors to our example FSM in parallel during the remainder of the modeling steps This approach will show the flexibility of rube One metaphor will in volve water tanks pipes and water and the other will involve gazebos walk ways and a person Both metaphors are conceptualized in 3 D Step 4 Define Mappings Develop Analogies The mappings between the water tank pipe metaphor and the FSM are simple e Water tanks represent states in our FSM When a water tank is full the FSM is in the state represented by that water tank Only one tank may be full at a time Since our FSM has three states we will need three water tanks Each water tank will correspond to a specific state in our FSM e Transitions in our FSM are represented by water pipes Water flows from one tank to another over a pipe that connects the two tanks to rep resent the activity a transition Since our FSM has three transitions we will need three water pipes Each water pipe will correspond to a spe cific transition in our FSM e The data transfer token implicit in our FSM is represented by water There is only one token so there is a constant volume of wa
5. alization Framework for Dy namic Models 2002 Web3D Conference in Monterey CA submitted 2001 M Najork Programming in Three Dimensions Ph D dissertation Univ of Illinois at Urbana Champaign 1994 T Kim and P A Fishwick Virtual Reality Modeling Language Templates for Dy namic Model Construction Enabling Technology for Sim Sci SPIE 01 Aero Sense Conference Orlando FL April 2001 G C Roman and K C Cox A Taxonomy of Program Visualization Systems IEEE Computer 26 12 1993 pp 11 24 M A Najork and M H Brown Obliq 3D A High Level Fast Turnaround 3D Animation System IEEE Trans on Vis and Comp Graphics 1 2 1995 pp 175 193 R M Donahue Industrial Plant Metaphor with a Change in Geometry http www cise ufl edu fishwick rube tutorial Fsm4 world4 wrl 2001 N Kohareswaran World with a Human Agent Metaphor http www cise ufl edu fishwick rube tutorial Fsm5 world5 wrl 2001
6. current pro liferation of customized skinz in window based graphical user interfaces GUIs The renewed focus on accommodating the individual in media and user inter faces suggests a corresponding accommodation of personal preference in model representation and by extension 3 D SV There may be some advantage to be gained from personalization in 3 D visualization To illustrate a frequent occurrence during the development proc ess is that one or more abstract data types or functions are created If a devel oper finds value in 3 D visualization and would like to visualize an abstract function such as a sorter he or she may arbitrarily decide to visualize it as a green pyramid Instead it may be possible to create a more elaborate visualiza tion for the sorter For example the developer might be able to visualize the sorter as an animated person who is sorting boxes If the developer uses the animated sorting person he or she has made an analogy between the abstract sorter and the concrete real world person If the sorter is visualized in this fash ion there is no need to memorize the previous mapping of the green pyramid to the sorter The visualization of the person and the analogy introduced now pro vide this mapping implicitly In effect the visualization provides a semantic cue as to the object s function This sort of visualization then may serve as a form of implicit documentation It would be difficult to support the argument tha
7. ding 3 D animations that consists of an interpreted language that is embed ded into a 3 D animation library 15 There are some similarities between rube and Oblig 3D The languages used in both systems for specifying graphics ob jects have similar structure expressive power animation and interactive capa bilities Both systems use interpreted languages for rube XML VRML X3D and etc so both are fast turnaround There are also some significant differ ences between rube and Oblig 3D The rube development system is web based and portable e g HTML XML VRML X3D while Oblig 3D is not e g X Windows Microsoft Windows Modula 3 Obliq VRML X3D and XML are not strictly OO languages while Obliq is It should be easier to create graphical structures especially compound structures in a free form environment in rube using third party tools that export VRML In addition geometric structures can be easily reused for any purpose in rube Sound can be incorporated as part of rube models while Oblig 3D does not mention this capability Finally rube and Obliq 3D were designed around somewhat divergent goals rube is more fo cused on aesthetics and modeling in a formal sense The Steps of the rube Modeling Methodology The rube modeling and visualization methodology proposed by Fishwick 4 consists of the following five steps 1 Choose system to be modeled This could be anything from a system in the real world e g the Eve
8. e dynamic behavioral model types are freely combined in OOPM through the process of multimodeling which glues together models of same or different type 5 An example of a multimodel based on a real world system might be the fol lowing Assume that a group of people is standing in a straight line in front of a single ticket booth The line is a simple queuing network QNET with a queue the line queued entities the people and a server the ticket booth Now assume that we would like to describe the state of each person waiting in the line as stopped moving or being served To model these states we could incorporate a finite state machine FSM within each person There would be three states in each FSM stopped moving and being served Events that are happening in the queuing network would trigger transitions between states in each person s FSM If the line is moving the FSMs for people in the line transi tion into the moving state When the line stops the FSMs transition into the stopped state If a person is the next in line for waiting for service that person s FSM will transition from stopped to moving to being served This completes the example multimodel which demonstrated a hierarchical arrangement of FSMs within entities that were part of a QNET The OOPM system has some other noteworthy features One feature is its 2 D GUI which facilitates model design controls model execution and provides 5 J F H
9. eling with developer defined visual and audible elements The use of 3 D metaphor based visualization lends rube models aesthetic and artistic aspects that are relatively novel in the realm of SV and it would be a notable achievement to blend SV with the creation of a work of art through the vehicle of 3 D metaphor An alternative course is to limit model visualization to the creation of diagrams composed of abstract geometric shapes and symbolic text In essence these shapes and text are wholly arbitrary forms of representa tion As such they generally lack intrinsic semantic content Additionally the generic nature of these shapes and text lessens their potential aesthetic impact These shortcomings may be ameliorated if a developer is allowed and encour aged by a framework like rube to embellish these generic entities with custom ized 3 D metaphor based visualizations We currently monitor related human focused empirical research and it is our ultimate aim to generate empirical research centered on the use of the rube development environment and modeling methodology Before this sort of un 15 J F Hopkins and P A Fishwick dertaking it is necessary to have an approximation of both the environment and the methodology Specifically we wish to avoid a catch 22 situation where experiments cannot be executed without entanglement of experimental results with issues related to tool quality and quality tools cannot be constructed
10. ement a 3 D programming GUI that for instance allows a user to construct a network of 3 D objects that would be parsed by the GUI to automatically generate an executable program such as Najork s CUBE 12 In addition unlike CUBE rube does not possess a formal 3 D syntax nor is it a set of 3 D representa tions of primitive data types and atomic operations Figure 1 rube s GUI 7 J F Hopkins and P A Fishwick One major distinguishing feature of rube s modeling architecture is that it separates geometry from inter object semantic relations 11 Any scene file which represents geometry and appearance can be used along with any model file which contains information about relations and behaviors of the model 11 The rube development environment allows users to either create or reuse ex isting 3 D objects for the scene file and allows users to create or reuse dynamic models for the model file 11 The freedom of defining and creating 3 D objects has been given completely to the model author 11 Objects can be personalized and made culturally or aesthetically meaningful 4 11 13 Placing rube in a Frame of Reference with Respect to Software Visualization To give readers a better idea of the characteristics of the rube framework we classify it according to the program visualization system taxonomy given by Roman and Cox 14 Within this taxonomy there are three possible roles to be played programmer a
11. gement of transitions that exist between the states Alternatively take this topology from a library Place this topology in the model file Either by hand or with a third party geometry modeling tool create geometric 3 D analogs for each component of the FSM that will be visualized Alternatively take these objects from a library In the case of our FSM we could create cylindrical water tanks or gazebos to rep resent states pipes or walkways to represent transitions and water or a person to represent the data transfer token Place these objects in the scene file Specify the animation behavior of the graphical components created in the previous step Alternatively take these behaviors from a library An example behavior for water tanks is the filling or emptying of the tanks with water An example behavior for the walkways is the move ment of the person over the walkways Place these behaviors in the model file Merge the scene and model files with the Model Fusion Engine s GUI interface 13 J F Hopkins and P A Fishwick The implemented water tank world authored by Donahue 16 is shown in Fig 3 The implemented gazebo world authored by Kohareswaran 17 is shown in Fig 4 s1 s3 s2 Figure 3 Example FSM with water tank metaphor applied Author R M Donahue Figure 4 Example FSM with gazebo metaphor applied Author N Kohareswaran 14 The rube Framework for Personalized 3 D Software Visualizati
12. ize the multimodel These original steps were derived before the current work in XML Our cur rent work assists the users in these steps as follows For step 2 there are a set number of dynamic mode types planned for rube and the formal XML schema specification for two of them FSM and FBM are underway Step 3 currently remains manual For step 4 there are guidelines but no programmatic assistance Step 5 includes significant assistance in the form of the Model Fusion Engine rube Example World The following world briefly addresses the high level development of a simple model and its visualization in rube Steps 1 Choose System to be Modeled We will specify a simple light bulb system that can be in three different states First we must connect the bulb by way of a ceramic base to the wall socket This state is represented by an initial state of disconnected Once the light is connected it moves to a second state of off From there it moves to on if a chain is pulled If the chain is pulled again the light goes off and so on 10 The rube Framework for Personalized 3 D Software Visualization Step 2 Select Structural and Dynamic Behavioral Model Types The system that we chose in the previous step can be modeled well with an FSM Before we begin the development of our FSM let us first give a basic formal definition A FSM is described by the set T U Y Q Q 5 where e Tis the time base T R rea
13. l numbers for continuous time systems and T Z integers for discrete time systems e Uis the input set that contains all possible values that can be used as input to the system e Y is the output set that contains all possible values that can be output by the system Q is the countable state set Q is the set of acceptable input functions 6 is the transition function 6 Q x Q gt Q is the output function Q gt Y A simple FSM that describes our light bulb system is shown in Fig 2 S1 repre sents disconnected S2 represents off and S3 represents on Connecting the bulb to the ceramic base activates the S1 S2 transition labeled with a 1 Pulling the chain to turn the light on and off alternately activates the S2 S3 and S3 gt S2 transitions both labeled with a 2 Figure 2 Example FSM Our FSM is defined as follows FSM T U Y Q Q 5 T Zot U 1 2 Y Q Q SI start state S2 S3 11 J F Hopkins and P A Fishwick e Q for to and 2 for all other T e amp O0xQ gt 0 e XQ gt Y In the first time step the FSM will change state from S1 to S2 Thereafter on each time step the FSM s state will alternate between S2 and S3 Step 3 Choose a Metaphor and or an Aesthetic Style Here it is likely that a user would choose a single metaphor to represent the system or perhaps a group of metaphors and sub metaphors to represent
14. m Visualization Effectiveness Journal of Vis Lang and Comp in press 3 P A Fishwick rube http www cise ufl edu fishwick rube intro index html 2001 4 P A Fishwick Aesthetic Programming Leonardo magazine MIT Press Cam bridge MA to be published 2002 5 R M Cubert T Goktekin and P A Fishwick MOOSE Architecture of an Object Oriented Multimodeling Simulation System Proc Enabling Technology for Sim Sci SPIE AeroSense 1997 Conf Orlando FL USA April 22 24 1997 pp 78 88 6 P A Fishwick SIMPACK Getting Started with Simulation Programming in C and C 1992 Winter Sim Conf Proc Arlington VA USA December 1992 pp 154 162 7 K Lee and P A Fishwick OOPM RT A Multimodeling Methodology for Real Time Simulation ACM Trans on Modeling and Comp Sim 9 2 1999 pp 141 170 8 P A Fishwick Simulation Model Design and Execution Prentice Hall Englewood Cliffs NJ 1995 448 pp 16 10 11 12 13 14 15 16 17 The rube Framework for Personalized 3 D Software Visualization P A Fishwick N H Narayanan J Sticklen and A Bonarini A Multi Model Ap proach to Reasoning and Simulation IEEE Trans on Syst Man and Cybern 24 10 1992 pp 1433 1449 P A Fishwick and B P Zeigler A Multimodel Methodology for Qualitative Model Engineering ACM Trans on Modeling and Comp Sim 2 1 1992 pp 52 81 T Kim and P A Fishwick 4 3D XML Based Visu
15. n the system If readers will indulge us we consider the terms software program and model to be more or less conceptually equivalent unless otherwise noted for the purpose of discourse in this chapter Likewise we con sider the terms software developer programmer and modeler to be more or less conceptually equivalent unless otherwise noted Modelers come to understand predict and analyze a system based on the models that they construct for it The model represents a key medium that links modelers to the phenomena Thus the model s representation plays an important role as an interface to its users Although historically there has been a rich vari ety of textual and diagrammatic approaches to model representation there has been little systematic accommodation of personal preference in these ap proaches Our culture is driven in part by economy of labor and materials and person alization is held back primarily for these economic reasons However today s economy is at a stage where personalization has become more feasible and some trends in personalization are developing in both media and human computer interfaces For our immediate purposes we do not draw a distinction between customization and personalization treating both as facets of aesthetic choice rube is a trademark of Paul A Fishwick and the University of Florida 3 J F Hopkins and P A Fishwick An example of personalization in human computer interfaces is the
16. nimator and viewer 14 A rube developer is both the programmer and animator and anyone may be a viewer At this time we con sider the primary viewing audience to be either the model author or someone who is familiar with modeling in the context of rube This slant may change in the future and we have been investigating both novice modelers and artistic communities as possible users audiences for the rube framework and its models Continuing with the axes of the taxonomy 14 e Scope rube does not automatically transform model code into page layouts such as flowcharts or statement level diagrams It is capable of showing model data and control states but the implementation of these capabilities is up to the programmer animator Since rube is primarily an event based system it is best adapted by programmers animators for relating model behavior e Abstraction rube is capable of direct structural and synthesized model representation However rube primarily encourages structural representation Again the implementation of these capabilities is up to the programmer animator It is possible to implement zooming capa bilities to provide low and high levels of abstraction to a user that is navigating throughout a world e Animation Specification Method rube relies heavily on annotation by the programmer animator Predefinition declaration and manipulation do no play a role in rube e Interface rube inherits its graphical capabili
17. on Summary Benefits of the rube Framework The rube framework has the potential to make building 3 D visualizations easier than is possible with other software visualization systems in direct proportion to 1 the use of libraries of prefabricated geometric models 2 the expressive power of VRML X3D and XML and 3 the ease of use of third party geometry modeling tools The issue of whether or not rube enables the creation of more effective visualizations depends heavily on the programmer animator and the viewer If the programmer animator is the viewer then benefits may be derived from self construction If the viewer is not the author then benefits may only exist when the author has used obvious and or traditional representation meth ods provided extensive text based explanations or provided interactive controls for the viewer These speculations are based on research mentioned in the intro duction to this paper 1 2 The rube framework s contributions to the field of software visualization are directly related to its progress toward the first two of its previously stated goals Specifically 1 To create a model design methodology and a software system that sup ports a separation of dynamic model specification from presentation and visualization 2 To work with the Fine Arts community in creating more personalized and aesthetic presentations The rube framework supports this effort by promoting the integration of mod
18. onment The rube development environment is implemented in XML eXtensible Markup Language and includes a 3 D web based GUI 3 that controls a Model Fusion Engine 11 The Model Fusion Engine supports the fusion of geometry models dynamic models e g FSM FBM and others as previously listed and their scripted behaviors 11 The fusion process merges a geometric scene file and a model file 11 The scene file contains a user defined VRML Virtual Reality Modeling Language world either created in a 2 D text editor or exported from other 3 D software such as CosmoWorlds or 3D Studio Max 11 The model file is a user defined XML file that defines connectivity between objects and the behavior of the dynamic model types 11 Each dynamic model is modularized and used as a separate library 11 When the Model Fusion En gine finishes merging the scene and model files it generates an X3D eXtensi ble 3D file 11 This file is then translated into a VRML file that can be 6 The rube Framework for Personalized 3 D Software Visualization displayed in a VRML browser such as such as Blaxxun Contact Parallel Graphics Cortona and CosmoPlayer 11 The GUI is shown in Fig 1 In the lower part of the window a user can specify or upload user defined scene and model files 11 In the upper part of the window the newly created 3 D dynamic model is displayed with a VRML browser 11 It is important for readers to note that rube does not impl
19. opkins and P A Fishwick 2 D output visualization 5 Another feature is a model repository that facili tates collaborative and distributed model definitions and that manages object persistence 5 The Goals of rube The rube framework and OOPM share many characteristics For example they both make use of the previously listed dynamic behavioral model types within a multimodeling framework However rube research and development R amp D moves OOPM concepts into the third dimension and expands on them Specifi cally the goals of rube R amp D are 1 To create a model design methodology and a software system that sup ports a separation of dynamic model specification from presentation and visualization 2 To work with the Fine Arts community e g university Digital Arts and Sciences programs in creating more personalized and aesthetic presentations The rube framework supports this effort by promoting the integration of modeling with developer defined visual and audible elements 3 To enable specification of dynamic models for use in a wide variety of systems needs one of which is programming and others are models used for simulation One physical manifestation of this goal is a pub licly available World Wide Web WWW based toolkit composed of reusable generic 3 D model components based on the basic dynamic behavioral model types along with a model repository composed of fully developed models The rube Development Envir
20. rglades ecosystem to a typical software system e g database 9 J F Hopkins and P A Fishwick 2 Select structural and dynamic behavioral model types Here modelers specify the dynamic behavioral model types to be used in designing the multimodel These include CM FSM FBM SDM and others as pre viously listed Next modelers specify the dynamics and interactions between the different models 3 Choose a metaphor and or an aesthetic style Here modelers develop their own custom metaphors for the phenomena that they are modeling It is preferable that these metaphors have some readily apparent rela tionship to the phenomena being modeled but the presence of such a relationship is not required by rube For example modelers may choose an architectural metaphor Within architecture are many differ ent aesthetic styles to choose from like Romanesque Baroque and Art Deco 4 Define mappings Develop analogies In this step the modeler develops a careful and complete mapping between the structural and dynamic behavioral model type components and the metaphorical and stylistic components Although the rube development environment itself does not specifically support the automatic or assisted mapping of a software system to a visualization it does offer guidelines for some common modeling and programming constructs 4 5 Create model Here the modeler combines the models and mappings generated in the previous to synthes
21. t the green pyramid visualization is preferable to the animated sorting person on grounds other than the additional effort it would take to produce the animated person Finally the extra effort required to produce a personalized 3 D visuali zation should decrease to a minimal level with time and advances in technology so that a cost benefit analysis should eventually become favorable There is some empirical evidence that shows the value of self construction in visualization For example the use of metaphor in diagrams has been shown to provide some mnemonic assistance which appears to be greatest when the user of the diagram constructs his or her own metaphor 1 In addition it has been empirically established that the process of actively constructing one s own visual representations is more beneficial than passively viewing someone else s visual representations 2 Fishwick 3 4 has been developing a modeling framework called rube in which users develop both static and dynamic 3 D model visualizations in paral lel with other modeling efforts What sets rube apart from similar work is that these visualizations can be highly customized by the user This chapter dis cusses rube s approach to modeling and representation To illustrate the rube modeling process a systematic example of model development is presented The example is a simple Finite State Machine Finally the benefits of the ap proach and future directions are discussed
22. ter to cor respond to the token This volume is just enough to fill one tank of wa ter and all tanks should have the same volume 12 The rube Framework for Personalized 3 D Software Visualization Similarly the mappings between the gazebo walkway metaphor and the FSM are simple Gazebos represent states in our FSM When the person is in a gazebo our FSM is in the state represented by that gazebo Since there is only one person only one state is active at a time In addition since our FSM has three states we will need three gazebos Each gazebo will correspond to a specific state in our FSM Transitions in our FSM are represented by walkways The person moves from one gazebo to another over walkways that connect the two gazebos to represent the activity of a transition Since our FSM has three transitions we will need three walkways Each walkway will cor respond to specific transition in our FSM The data transfer token implicit in our FSM is represented by the per son Step 5 Create Model Here is a basic outline of the steps involved in creating the models 1 Specify the basic FSM components such as state and transition Alter natively take these components from a library Place these in the model file Note these components should be generic and be as non specific as possible to the model currently under construction Specify the FSM topology That is specify the number of states in the FSM and the arran
23. ties from VRML and its successor X3D Thus it can specify simple objects compound objects visual events and worlds Within worlds both absolute and constraint based positioning are permitted Multiple worlds i e separate win dows with separate objects that all represent alternate views of the 8 The rube Framework for Personalized 3 D Software Visualization same model are possible but are not a not a focus of rube Interaction with the world by the viewer is managed through the VRML browser and is programmer animator defined Interactive capabilities are often implemented in the form of predefined controls These controls can be embedded in the image e Presentation rube is extremely flexible concerning interpretation of graphics Any accompanying text based explanations must take into account the intended audience Since the audiences for rube models are not yet well defined we leave this issue to programmers animators Programmers animators need to be aware that others may not easily grasp their display customizations perhaps performed without regard to related conventional or obvious styles of presentation Accompa nying detailed text based explanations may be necessary A rube visu alization is capable of showing explanatory events and orchestrations The incorporation of aesthetic visual and audible elements in models are encouraged by rube Najork and Brown s Oblig 3D is a high level fast turnaround system for buil
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