Improving visual impact analysis

Visual impact analysis is a software visualisation technique that lets software maintainers judge the impact of proposed changes and plan maintenance accordingly. An existing CASE tool uses a directed acyclic graph display derived from decomposition slicing of a program for visual impact analysis. In this paper, we analyse the graph display and show that it is semantically ambiguous and fails to show important information. We propose requirements for an improved display based on a definition of "interference" between variables in a maintenance context. The design for a new display is presented with a series of examples to illustrate its effectiveness. The display is focused on providing a straightforward method to analyse the impact of changes.