Finding structures in multi-type code couplings with node-link and matrix visualizations

Software systems are often modeled and visualized as graphs in order to understand their higher-level structure: code entities are connected by dependencies or couplings. However, when only considering one type of code coupling such as method calls, the understanding gained stays limited to this specific aspect. Encoding multiple types of code coupling in the graph promises to broaden the understanding. Different approaches already exist for visually discerning those types in graph diagrams. In this paper, we study two of these techniquesa node-link and a matrix approach-in a realistic scenario where the classes and interfaces of a system are connected by six different types of code coupling. The explorative user study that we conducted with interactive versions of the two visualizations focuses on getting an insight on how software developers use the visualizations for understanding an unknown system. We classified typical visual structures that the participants were able to identify and connected these structures to software engineering problems. Despite the fundamental difference in approach, the participants identified the same graph structures targeting similar tasks with both visualizations.