ArchView - Analyzing Evolutionary Aspects of Complex Software Systems

Large and complex software systems are confronted with continuous changes during all stages in their life comprising development, maintenance, migration, and retirement. On the one side these changes are mandatory to guarantee the success of a software system but on the other side changes affect the architecture and design of a software system. Therefore, a continuous observation and analysis of the architecture and the design is needed to early identify shortcomings and resolve them. In this dissertation we propose the ArchView approach that focuses on the analysis and evaluation of software modules regarding their structural and evolutionary characteristics. Software modules are architectural elements that are implemented in source files, classes, or aggregations of them. The primary objective of our approach is to extract higher-level views of software modules and their dependency relationships that allow the spectator to identify structural and evolutionary shortcomings. For the analysis of the structural and evolutionary characteristics of software modules ArchView uses software metrics and coupling relationships. Software metrics quantify the size, complexity, coupling degree, modification and problem frequency of software modules. Coupling relationships show change as well as implemented dependency relationships between modules. Both, metrics and coupling relationships are computed for a number of subsequent source code releases giving insights into the evolution of modules. For the identification of structural and evolutionary shortcomings ArchView introduces a graph representation technique that is based on the principle of measurement mapping. Metric values are mapped to graphical attributes highlighting in particular modules and dependency relationships with noticeable structural and evolutionary characteristics. To handle the various characteristics we present a number of different view configurations that we implemented in a prototype tool. They can be extended and used by engineers in everyday analysis tasks. The evaluation and validation of the ArchView approach and its different view configurations is done with the large open source project Mozilla. We focus on the analysis of the content and layout modules with different higher-level views. Resulting views clearly show the usefulness of ArchView to visualize structural and evolutionary characteristics of Mozilla modules and point out a number of shortcomings in their design.