PROCEDURE BASED GENERALIZED INTERACTIVE SYSTEMS

This work describes a language for writing interactive systems that are independent of the applications that they service. This generality is based on application-specific information describing the command set of the application to the interactive processer. The model for this command set description is the procedure mechanism of a strongly-typed language called GINTAC, which is based on PASCAL and ADA. GINTAC allows the compiler\u27s symbol table information to be made available at run time via a construct called a symbolic expression. This information which describes procedures, variables and data types can then be used as the comand set definition by an interactive processer. In addition, interaction-specific information can be attached to declared symbols to enrich the expressiveness of this interface. Primitives are provided in the language to obtain access to the information supplied by a symbolic expression. It is also possible to create expressions at run time which can be used to execute the application\u27s commands. Two such general interactive processers were designed based on the GINTAC language. The first is a general expression parser. It is shown how the command languages of several timesharing systems could be implemented using it. The second interactive processer supports a graphical interaction. It provides automatic menu generation, function button management and automatic user feedback. It is shown how the picking of objects from a display screen can be used to specify operands for expressions. In addition, it is shown how the strong typing of the expressions can resolve ambiguity that occurs when pointing at heirarchicly defined pictures. It is also shown how this system can be used to implement several graphical applications drawn from the literature. These two systems serve only to demonstrate this technique not to define the full extent of its capabilities