Visualization of program dependence and slices

Abstract

The program dependence graph (PDG) itself and the computed slices within the program dependence graph are results that should be presented to the user in a comprehensible form, if not used in subsequent analyses. A graphical presentation would be preferred as it is usually more intuitive than textual ones. This work describes how a layout for the PDGs can be generated to enable an appealing presentation. However, experience shows that the graphical presentation is less helpful than expected and a textual presentation is superior. Therefore, this work contains an approach to textually present slices of PDGs in source code. The innovation of this approach is the fine-grained visualization of arbitrary node sets based on tokens and not on complete lines like in other approaches. Furthermore, a major obstacle in visualization and comprehension of slices is the loss of locality. Thus, this work presents a simple, yet effective, approach to limit the range of a slice. This approach enables a visualization of slices where the local effects stand out against the more global effects. A second, more sophisticated approach visualizes the influence range of chops for variables and procedures. This enables a visualization of the impact of procedures and variables on the complete system.