Context-Aware Digital Documents Described In A High-Level Petri Net-Based Hypermedia System Jin-Cheon Na and Richard Furuta Department of Computer Science Center for the Study of Digital Libraries Texas A&M University September 14, 2000

2 Contents n Introduction n Research Objectives n Related Work n caT (Context-Aware Trellis) n Future Work n Conclusion

September 14, Introduction n Challenges for digital document systems –Users are in dynamically-changing environments. –Users’ information requirements are dynamically- changing in different environments –Systems need to support flexible user adaptation to a changing environment –Mobile devices support environmental sensors GPS receivers, active badges, electronic compasses, super sensors, etc.

September 14, Introduction n The need for context-awareness –Context is any information that can be used to characterize the situation of the current user. location, orientation, objects nearby, temperature, time of day and time of year, etc. –A system is context-aware if it uses context to provide relevant information and/or services to the user. (definition by Dey and Abowd)

September 14, Introduction n Context-Aware Applications –Mobile tour guides (Cyberguide, Stick-e notes) –Office awareness systems (the active badge location system, Teleporting) –Context-based retrieval applications (conference assistant) –Context-aware application building tools (the context toolkit)

September 14, n The main goal of this research –Provides context-aware hypertextual information delivery by incorporation of dynamically-changing information from the external environment n Example: a context-aware digital library –A full version of a Web document to its on-campus patrons and a limited one to its off-campus patrons –More detailed documents for reference material located on the current floor than for other floors –Some documents available for general use outside of working hours Research Objectives

September 14, Research Objectives n The methods caT –Develop caT (called caT, for Context-Aware Trellis), a context-aware hypertext model and associated tools –A context-aware hypertext model high-level Petri net features; user modeling concept fuzzy knowledge handling –Associated tools flexible information presentation tool; authoring tool analysis tool (verification and validation) –caT extends Trellis, a Petri-net-based hypertext system, in support of context-awareness

September 14, Related Work n Petri Net –A uniform environment for modeling, formal analysis, and systematic building of systems –A bipartite graph Before Fire After Fire

September 14, Related Work n High-Level Petri Nets –Allow for tokens to have distinct identity; a token can be a composite object carrying data. –Provide much better structuring facilities than basic nets –caT uses the high-level Petri nets. n Trellis –Supports structure and browsing semantics of hypertext documents using colored timed Petri nets –Supports the specification of access control –Supports time-based hypertext browsing

September 14, Related Work n Trellis (continued) –Foundation work in [Stotts and Furuta, 1989] “Petri-net-based hypertext: Document structure with browsing semantics”, ACM TOIS n Adaptive Hypermedia Systems –Definition by Brusilovsky “All hypertext and hypermedia systems which reflect some features of the user in the user model and apply this model to adapt various visible aspects of the system to the user.” –Major applications are educational hypermedia systems –caT provides simple user modeling.

September 14, caT n Context-aware hypertext model –Structured tokens each colored token caries its own local variable/value pairs represent dynamic and environmentally changing data –User modeling each colored token can have a link to a user- modeling profile represents less dynamic and user’s profile data –Link adaptation conditional statements on transitions –determine the threshold values for transition firing

September 14, caT: A sample caT net (a) Before Fire After Fire r r Select black r r time: (20, 100) Cond:(r.w.class ==‘oncampus’ || r.u.userType == ‘faculty’) Black:{(class,‘oncampus’) (user, ‘tom’) (enterTime, ‘’)} Pink: {(class,‘offcampus’) (user, ‘david’) (enterTime, ‘’)} Black:{(class,‘oncampus’) (user, ‘tom’) (enterTime,’15:30’)} Pink:{(class,‘offcampus’) (user, ‘david’) (enterTime,’’)} expr:(r.w.enterTime = send(time1.currTime() )

September 14, caT: A sample caT net (b) Select black time: (20, 100) Cond: (r:1.w.class ==‘oncampus’ || r:1.u.userType == ‘faculty’) Black:{ class,‘oncampus’) (user, ‘tom’) (enterTime, ‘’)} Pink: { (class,‘offcampus’) (user, ‘david’) (enterTime, ‘’)} Black:{ } Pink: { } Before Fire r:1 r:2 r:1 r:2 After Fire r:1 r:2 r:1 r:2 Black:{ class,‘oncampus’) (user, ‘tom’) (enterTime,’15:30’)} Pink: { class,‘offcampus’) (user, ‘david’) (enterTime,’’)} Black:{ } Pink: { } expr:(r:1.w.enterTime = send(time1.currTime() )

September 14, caT n Fuzzy logic tool integration –Fuzzy logic engine: Matlab Fuzzy Logic Toolbox invoked on transition firing –A sample rulebase If (time is day) and (distance is close) then (accessRight is high) If (time is day) and (distance is middle) then (accessRight is middle) If (time is day) and (distance is far) then (accessRight is low) If (time is not day) then (accessRight is high) n Flexible Information Presentation (FIP) tool –Supports Web-based browsing –Uses a template file (Meta file) a virtual dynamic composite node

September 14, caT n Example: a context-aware digital library –Provides a full version of a digital library to its on- campus patrons and a limited one to its off- campus patrons –Faculty members off-campus retain access to the full version –Because the page includes a real-time help desk, only the limited version is available outside of normal operating hours –Context information current user’s location, access time, occupation, incoming IP address, etc.

September 14, caT: Petri net of a simple digital library tour

September 14, caT: Digital library tour for on-campus user Context-aware display (a) Current net state n Initial Page

September 14, caT: Digital library tour for on-campus user n After On_Campus_Service clicked Context-aware display (b) Current net state

September 14, caT: Digital library tour for on-campus user n After LibCat clicked Context-aware display (c) Current net state

September 14, caT: Digital library tour for on-campus user n After Finish clicked Context-aware display (d) Current net state

September 14, caT: Architecture Applet WWW Browser HTTP server Server (in Java) Shared Library (in C) Thread 1 Thread n …... Socket HTTP Client Server JNI RPC JavaScript Web Server Interface (Web page display) Information Server Interface (Petri net related transactions) Information Servers (Petri Net Engines) Thread 1 …... Thread n Store Documents Retrieve Documents Web Documents

September 14, Future Work n Authoring tool –Supports structured authoring top-down or bottom up design –Reduces graphical complexity problems –Supports reasonably large sizes of applications –The method: Hierarchical net subnets used as templates, like functions token value passing between subnets uses substitution transitions

September 14, Future Work n Authoring tool (current prototype)

September 14, Future Work n Verification and validation –Verification of the behavioral characteristics of hypertext systems reachability of nodes, dead links, home property, performance (navigation time), etc. –Analysis tools generate reachability trees (or occurrence graphs) and verify behavioral properties

September 14, Conclusion n Introduced a context-aware hypertext model and associated tools n Showed the potential usability of context- aware hypertext systems n Research work continues in order to enhance the usability of the caT model

September 14, Further Questions & Suggestions Jin-Cheon Na and Dr. Richard Furuta {jincheon, Department of Computer Science Center for the Study of Digital Libraries Texas A&M University

September 14, caT n A sample template file some descriptive text ….. some descriptive text …..

September 14, caT n Example: a simple image gallery tour –Provides a full version (image-based) of a Web page to its on-campus patrons and a limited (text- based) one to its off-campus patrons –Faculty members off-campus retain access to the full version –Context information current user’s location, access time, occupation, incoming IP address, etc.

September 14, caT: Petri net of a simple image gallery tour

September 14, caT: A simple image gallery tour Context-aware display

September 14, Future Work n Hierarchical Net ClassifyUser WebTraverse Net#1 (ClassifyUser -> CalcTime, WebTraverse -> Branch) Substitution Transition Subnet invocation Net#1 Branch CalcTime Check_Status