Petri nets: an introduction
Visual programming, programming by example, and program visualization: a taxonomy
CHI '86 Proceedings of the SIGCHI Conference on Human Factors in Computing Systems
HAM: a general purpose hypertext abstract machine
Communications of the ACM
Abstraction mechanisms in hypertext
Communications of the ACM
Petri-net-based hypertext: document structure with browsing semantics
ACM Transactions on Information Systems (TOIS)
Petri Net Theory and the Modeling of Systems
Petri Net Theory and the Modeling of Systems
Visual Languages: A Tutorial and Survey
IEEE Software
Subdocument invocation semantics in collaborative hyperdocuments
WET-ICE '95 Proceedings of the 4th Workshop on Enabling Technologies: Infrastructure for Collaborative Enterprises (WET-ICE'95)
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The visual programming aspects of Trellis hypertext documents are described. A hypertext is a non-linearly organized, browsable information structure. The importance of browsing distinguishes hypertext from other network information systems. The possible experiences a user may have when interacting with a hypertext are as important as its form. Further, these browsing semantics should be an inherent characteristic of a document, not of the implementation that allows browsing. In essence, a hypertext is an active entity that has a visible behavior, not a static entity that is manipulated by external means. The Trellis model employs the dual nature of Petri nets to formally express both aspects of a hypertext in one structure. A Petri net is a bipartite graph, so it captures the linked structure of relationships among information elements. It is also an automaton, having an execution state and state transition rules, thereby formally capturing the interactions between reader and document. In this report, we define the temporal semantics of the Trellis model and illustrate them with a prototype hypertext system called @aTrellis. This environment joins timed events and active computing engines into a dynamic, parallel browsing structure. In @aTrellis, hypertext authoring is visual programming for a temporally-synchronized, visual outcome-temporal hyperprogramming.