A new approach for visualizing UML class diagrams

UML diagrams have become increasingly important in the engi-neering and reengineering processes for software systems. Of par-ticular interest are UML class diagrams whose purpose is to dis-play class hierarchies (generalizations), associations, aggregations, and compositions in one picture. The combination of hierarchi-cal and non-hierarchical relations poses a special challenge to a graph layout tool. Existing layout tools treat hierarchical and non-hierarchical relations either alike or as separate tasks in a two-phase process as in, e.g., [Seemann 1997]. We suggest a new approach for visualizing UML class diagrams leading to a balanced mixture of the following aesthetic criteria: Crossing minimization, bend mini-mization, uniform direction within each class hierarchy, no nesting of one class hierarchy within another, orthogonal layout, merging of multiple inheritance edges, and good edge labelling. We have realized our approach within the graph drawing library GoVisual. Experiments show the superiority to state-of-the-art and industrial standard layouts