This paper describes Gyacc (graphical yacc), a tool we have developed to support a graphical approach to developing languages with parser generators such as yacc. Gyacc is an interactive environment which supports the construction of context-free grammars, and provides the user with the ability to study yacc-generated parsers. We are strongly convinced that to fully teach and understand the details of a generated parser, the user or student must see it in operation. Gyacc accomplishes this by providing a set of animations which the user can select to observe different aspects of the parser as it executes.

Object-Oriented programming is a powerful means of developing large complex systems. In this paper we address the need to understand the behavior of objects in order to facilitate code sharing and reusability. We describe GraphTrace, a tool we have developed that has allowed us to experiment with new ways of visualizing the dynamic behavior of object-oriented programs. Based on our experience with the GraphTrace tool we suggest that being able to present many different views of an object-oriented system and then animating these views concurrently represents a powerful means for understanding such systems.

This paper describes a new methodology for specifying and constructing complex interaction dialogs for the design of user interfaces. The method is new in that it promotes a decomposition of the interaction in terms of events in AND/OR graphs called Event-Decomposition Graphs (EDG). These Event-Decomposition Graphs can be progressively refined to capture the detailed semantics of the dialog. Multithreaded interaction can be composed by joining several Event-Decomposition Graphs together in a systematic way. In this paper we present a design tool for specifying and analyzing Event-Decomposition Graphs, and show that the combination of the notation and tool combines many of the capabilities of Context-Free Grammar- and Event-Notations while still providing the graphical view of Transition Network diagrams.