How to visualize directed graphs: A user study

Overloaded Orthogonal Drawing is a recent graph visualization paradigm that resembles classical orthogonal drawings, but is specifically tailored to directed graphs of arbitrary vertex degree. Its properties suggest that it can be applied to perform visualization-based tasks more effectively than other related paradigms. In this paper we investigate the usability of Overloaded Orthogonal Drawings against classical Orthogonal Drawings, Hierarchical Drawings, and Matrix-based Representations. All four paradigms are applied to visualize directed graphs. The results reveal a clear advantage in using Overloaded Orthogonal Drawings based on a set of common user's tasks, and most of the results are statistically significant. More in general, we observed that node-link representations outperform matrix-based representations for most of the proposed tasks on the given set of instances.