1. Richard Furuta furuta@csdl.tamu.edu Texas A&M University Center for the Study of Digital Libraries and The Department of Computer Science Firing a transition (following a link) Link Choice Join Fork Counter 3 Petri net constructs as hypertext features Access Control Active Place Token Inactive Place Enabled Transition (contents are displayed) (representation of user) (link can be followed) (contents are hidden) Disabled Transition Overview caT Introduces context-awareness in Trellis caT hypertexts respond to —Characteristics of users —Characteristics of environment —Repeated viewing —Passage of time —Activities of other users Formal, Petri net-based specification Places map to content, transitions to links Multi-user, multi-browser hypertext documents Specifies the browsing behavior of hypertexts Separates —structure from content —presentation from content Formality allows analysis of structure Colored, timed Petri nets —Colors represent users or roles —Timed nets can browse themselves Trellis Resource Realizer Resources Text, images, audio,video,etc Resources Request Resources Abstract resources handle and data format preferences Resources or pointer to resources Information server (Petri net Engine) Browser Manger Global Data store User Models, Petri net definition files, etc Server (linux) Http Subsystem Services Clients Devices Browser Coordinator Web Browser xtb Authoring Tool Anaysis Tool Image Browser Text Browser Browser Coordinator Desktop (Windows) PDA Desktop (linux) Server maintains the state of browsing Browsers render the information content Multiple clients can reflect the state of browsing to users —Collaborative browsing—Various users may view and navigate a hypertext in parallel Browsers may join or leave during a browsing session without affecting other browsers caT supports media-specific browsers System Architecture xTed: caT Authoring Tool canvas move to first title arc place transition cut label fire auto fire transition move token record play stop clear move to last forward backward token colors Image Browser Text Browser Web Browser ( Composite representation of text and images ) Selector Audio/Video Browser Browsers Current Directions Browser Development To support new media types—we currently support text, images, audio and video Understanding and addressing issues in simultaneous presentation of multiple audio/video elements To support a variety of behaviors, representations and metaphors—spatial browser Large hypertext Development Support Identification of higher-level authoring specifications Libraries of these structures will enable uniformity of structure across larger-sized hypertexts Parallel Browsing via Multiple Devices Find mechanisms to flexibly display content over different devices Customize the content and media type for achieving optimal effect on the target device Allow effects of user actions to propagate across devices Examples Hypertexts that display different content at different times of the day - Outside of working hours, links to light reading may augment a collection of job-related reference materials Hypertexts that use different presentation mechanisms for different types of display - Customized text-based browser for readers with slow internet connections - Web-based interface for external readers - Audio browser for readers using cell phones Hypertexts that reflect the material seen previously - Rereading may change the content to include more details Hypertext that provide different services depending on availability of other users - Clicking on a “help” links may direct a reader to a human subject expert she is not occupied but to a computer-based reference database otherwise - Collaborative browsing behavior may be different than when a user browses the hypertext alone