A commonly used strategy to address the scalability challenge in object-oriented reverse engineering is to synthesize coarse-grained representations, such as package diagrams. However, the traditional coarse-grained representations are poorly suited to object-oriented program comprehension as they can be difficult to map to the domain object models, contain little real detail, and provide few clues to the design decisions made during development.

In this paper, we propose a hybrid model of objectoriented software that blends the use of classes and entities at different levels of granularity. Each coarse-grained entity represents a set of software objects, and contains the complete static description of the objects it represents. This hybrid model allows maintainers to understand objects as independent units, and focus on the their external properties and their interrelationships at different levels of granularity. We show the usefulness of the hybrid model to program comprehension by means of an exploratory case study.