This paper describes how to use statecharts to model hypertext. Statechart is a formal graphical model based on state transition diagram and hypergraph. The statechart model is compared with other models for hypertext based on simple node-and-link graph, first-order logic formulae, hypergraph, and petri net. The features of statecharts relevant to the modeling of hypertext are described. Statecharts for the common features in frame-based and scrolling-based hypertext are given. Then statecharts are used to model the various buttons supported in a real-life production hypertext system, Guide (both the Unix version and the version marketed by Owl International Inc.). These examples illustrate that statechartscan be used to abstract the structure from the content of hypertext, and to model the structure and the browsing semantics of hypertext clearly and vividly.
This paper describes an implementation of a system for programming using structured charts with interactive graphical support. It provides a graphical editor for the user to interactively build and edit programs using Nassi‐Shneiderman diagrams (NSD)1 as the structured control constructs of logic flow. It can interpret a program in NSD chart form, and the execution sequence of the NSD is displayed at a graphical terminal. On‐line debugging and testing facilities are available which allow the user to examine and modify the program under execution. The system has been designed with the aim of supporting the development, debugging, testing, documentation and maintenance of programs in the same environment.
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