Design Patterns: A Round-trip

Design patterns are of major interest to increase software quality and abstraction level. However, design patterns are difficult to choose, to apply, and to recover. We propose a set of tools to use design patterns in a round-trip fashion. We define a meta-model to describe design patterns. This meta-model is specifically oriented towards design patterns instantiation and detection. We develop a source-to-source transformation engine to modify the source code to comply with design patterns descriptions. Meanwhile, we use an explanationbased constraint solver to detect design patterns in source code from their descriptions. With these tools, we hope to offer a mean to apply and to recover design patterns without overhead for the developers. ∗This work is partly funded by Soft-Maint – 4, rue du Château de l’Éraudière – 44 324 Nantes – France. †This work is partly funded by Object Technology International Inc. – 2670 Queensview Drive – Ottawa, Ontario, K2B 8K1 – Canada. 1 Problems Developing quality code is a major concern for the software community. Producing bug-free, extensible, and adaptable [Tok99] code is a hard task that requires skills, experience, and a deep understanding of the structure and behavior [RD99] of the software under development and of its context. The first problem encountered when developing quality code is in understanding the legacy of previous developments. As Enzo Torresi put it, in the Bits and Bytes column of the San Jose Mercury News (November the 15th, 1990; cited in [Pot90]): The reason God was able to create the world in seven days is that he did not have to worry about the installed base. An experienced programmer can often reconstruct much of the hierarchy of a program’s design by recognizing commonly used data structures and algorithms, and by knowing how they typically implement high-level abstractions [RW90]. However, This paper has been accepted at the workshop for PhD Students in Object-Oriented Systems at ECOOP 2001