Visualizations of Evolving Graphical Models in the Context of Model Review

Abstract

Code reviewing is well recognized as a valuable software engineering practice for improving software quality. Today a large variety of tools exist that support code reviewing and are widely adopted in open source and commercial software projects. They commonly support developers in manually inspecting code changes, providing feedback on and discussing these code changes, as well as tracking the review history. As source code is usually text-based, code reviewing tools also only support text-based artifacts. Hence, code changes are visualized textually and review comments are attached to text passages. This renders them unsuitable for reviewing graphical models, which are visualized graphically in diagrams instead of textually and hence require graphical change visualizations as well as annotation capabilities on the diagram level. Consequently, developers currently have to switch back and forth between code reviewing tools and comparison tools for graphical models to relate reviewer comments to model changes. Furthermore, adding and discussing reviewer comments on the diagram level is simply not possible. To improve this situation, we propose a set of coordinated visualizations of reviewing-relevant information for graphical models including model changes, diagram changes, review comments, and review history. The proposed visualizations have been implemented in a prototype tool called Mervin supporting the reviewing of graphical UML models developed with Eclipse Papyrus. Using this prototype, the proposed visualizations have been evaluated in a user study concerning effectiveness. The evaluation results show that the proposed visualizations can improve the review process of graphical models in terms of issue detection.