Refactoring-safe modeling of aspect-oriented scenarios

Aspects use pointcut expressions to specify patterns that are matched against a base model, hence defining the base locations to which aspects are applied. The fragile pointcut problem is well-known in aspect-oriented modeling, as small changes in the base may lead to non-matching patterns. Consequently, aspects are not applied as desired. This is especially problematic for refactoring. Even though the meaning of the model has not changed, pointcut expressions may no longer match. We present an aspect-oriented modeling technique for scenarios that is refactoring-safe. The scenarios are modeled with Aspect-oriented Use Case Maps (AoUCM), an extension of the recent ITU standard User Requirements Notation. AoUCM takes the semantics of the modeling notation into account, thus ensuring pointcut expressions still match even after, for example, refactoring a single use case map into several hierarchical maps. Furthermore, AoUCM allows the composed model to be viewed without having to resolve complex layout issues. The general principles of our approach are also applicable to other aspect-oriented modeling notations.