Exploring Inter-Module Relationships in Evolving Software Systems

Many of the existing approaches to reverse architecting - the reverse engineering of the architecture of software systems - are based on software exploration tools which provide interactive ways of exploring the system. These tools start with high-level views of the system and refine them with drill-down techniques applied on the high-level entities such as modules and packages, leaving aside valuable information contained in the dependencies between them. In this article we argue that the visualization of inter-module relations bears great potential for supporting the understanding of large evolving software systems. We present two concrete examples of such visualizations. The first, the semantic dependency matrix is a technique for displaying details about a dependency between two modules which groups together classes with similar behavior. The second, the edge evolution film-strip presents the evolution of an inter-module relation through multiple versions of the system. Based on our experience with the edge evolution film strip, we propose a pattern language for inter-module relationships. We exemplify both the visualizations and the pattern language with examples from two large open source software systems