Reduction of Visual Complexity in Dynamic Graphs

Graphs are used extensively in software visualization to represent both static aspects of software structure and dynamic aspects of execution-time behavior. However, for realistic subject software systems, there are far too many nodes and edges in the displayed graphs to be comprehensible to an end user. Further, for presentation of dynamics, continual change and redisplay of such large graphs is too demanding for conventional workstation computational resources. This paper poses the problem of "reduction" or "abstraction" in dynamically changing graphs, and proposes a combination of techniques that can be used to reduce the visual complexity of a graph, without obscuring the significant information that it was meant to convey. The abstract graph can be comprehended more readily and it changes far less frequently than the full graph. As well, when the abstract graph does change, it requires far less computation for layout and redisplay. These abstraction techniques are illustrated by way of examples showing their use in systems for visualization of objekt-oriented and multi-layer software systems