Richard Furutafuruta@csdl.tamu.edu

Texas A&M UniversityCenter 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

AccessControl

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

Resource Realizer

ResourcesResourcesText, images, audio,video,etcText, images, audio,video,etc

Reso

urc

es

Reso

urc

es

Request

R

eso

urc

es

Request

R

eso

urc

es

Abstract resources handle and data format preferences

Abstract resources handle and data format preferences

Resources or pointer to resources

Resources or pointer to resources

Information server (Petri net Engine)Information server (Petri net Engine)

Browser MangerBrowser Manger

Global Data storeGlobal Data store

User Models, Petri net definition files, etc

User Models, Petri net definition files, etc

Server (linux)Server (linux)

Http SubsystemHttp Subsystem ServicesServices

ClientsClients

DevicesDevices

Browser CoordinatorBrowser Coordinator

Browser CoordinatorBrowser Coordinator

Web BrowserWeb Browser

xtbxtb

Authoring ToolAuthoring Tool

Anaysis ToolAnaysis Tool

Image BrowserImage Browser

Text BrowserText Browser

Browser CoordinatorBrowser Coordinator

Desktop (Windows)Desktop (Windows)

PDAPDADesktop (linux)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 ToolxTed: caT Authoring Tool

canvascanvas

move to firstmove to first

titletitle

arcarc

placeplace

transitiontransition

cutcut

labellabel

firefire auto fireauto fire

transitiontransition

movemove

tokentoken

recordrecord playplay

stopstop clearclear

move to lastmove to last

forwardforwardbackwardbackward

token colorstoken colors

Image Browser Image Browser

Text BrowserText Browser

Web Browser Web Browser (Composite representation

of text and images)

SelectorSelector

Audio/VideoAudio/VideoBrowser

Browsers

Current DirectionsBrowser 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