Type Highlighting: A Client-Driven Visual Approach for Class Hierarchies Reengineering

Polymorphism and class hierarchies are key to increasing the extensibility of an object-oriented program but also raise challenges for program comprehension. Despite many advances in understanding and restructuring class hierarchies, there is no direct support to analyze and understand the design decisions that drive their polymorphic usage. In this paper we introduce a metric-based visual approach to capture the extent to which the clients of a hierarchy polymorphically manipulate that hierarchy. A visual pattern vocabulary is also presented in order to facilitate the communication between analysts. Initial evaluation shows that our techniques aid program comprehension by effectively visualizing large quantities of information, and can help detect several design problems.