A design pattern is realized in various forms depending on the context of the applications. There has been intensive research on detecting pattern instances in models and in implementations. However, little work addresses variations of pattern realization. This paper describes an approach for evaluating conformance of pattern variations. This approach uses a divide-and-conquer strategy to evaluate the structural conformance of a UML class diagram to the solution of a design pattern. A design pattern is specified in an extension of the UML that defines the pattern in terms of roles. To demonstrate the approach, we use the Visitor pattern and two case studies of a price calculator and a word processor. We also present a prototype tool that supports the approach.

Abstract. In order to retrieve, select and apply design patterns in a tool-supported way, we suggest to construct and document a problemcontext pattern that reflects the essence of the problems that the design pattern is meant to solve. In our approach, software engineers can choose examples of source code or UML models from the special domains that they are experts in. We present a method that enables software engineers to describe the transformation from a problem-bearing source model to an appropriate solution model. Afterwards, the inverse of that transformation is applied to the UML solution model of the existing design pattern, resulting in an abstract problem-context pattern. This pattern can then be stored together with the solution pattern in a pattern library. The method is illustrated by deriving a problem-context pattern for the Observer design pattern.