ENHANCED GRAPH MODELS IN THE WEB - MULTI-CLIENT, MULTI-HEAD, MULTI-TAIL BROWSING

One key to the wide and rapid acceptance of the World Wide Web is the simplicity of its model. We see this in its short-lived connections an d generally stateless servers, as well as in the relationship between nodes (HTML pages) and embedded links. Though these factors contribute to the Web's success, they also come at a cost: precise control of ho w documents are presented to the user is beyond this basic model. Rich er graph models permit authors to ''program'' the browsing behavior th ey want readers to see by turning the hypertext into a hyperprogram wi th specific semantics. Multiple browsing streams can be started under the author's control and then kept in step through the synchronization mechanisms provided by the graph model. Our current work adds a Seman tic Web Graph Layer (SWGL) which allows dynamic interpretation of link and node structures according to graph models. As a motivating exampl e of the utility of the SWGL, we have chosen to implement the graph mo del for Colored Petri Nets (CPNs). The previous MMM project [6] implem ented a limited subset of the Petri net model to give Web authors the ability to control concurrency and synchronization in a single reader' s browsing session. CPNs extend this protocol to give control of multi ple readers in a like fashion. This paper details the SWGL and its arc hitecture, some sample protocol implementations, and the latest extens ions to MHTML [6] that were necessary to support these enhancements.