Aspectual Mixin Layers: Aspects and Features in Concert

Feature-Oriented Programming (FOP) decomposes complex software into features. Features are main abstractions in design and implementation. They reflect user requirements and incrementally refine one another. Although, features crosscut object-oriented architectures they fail to express all kinds of crosscutting concerns. This weakness is exactly the strength of aspects, the main abstraction mechanism of Aspect-Oriented Programming (AOP). In this article we contribute a systematic evaluation and comparison of both paradigms, AOP and FOP, with focus on incremental software development. It reveals that aspects and features are not competing concepts. In fact AOP has several strengths to improve FOP in order to implement crosscutting features. Symmetrically, the development model of FOP can aid AOP in implementing incremental designs. Consequently, we propose the architectural integration of aspects and features in order to profit from both paradigms. We introduce aspectual mixin layers (AMLs), an implementation approach that realizes this symbiosis. A subsequent evaluation and a case study reveal that AMLs improve the crosscutting modularity of features as well as aspects become well integrated into incremental development style