Contract-Aware Feature Composition

Feature-oriented programming is a paradigm to develop software product lines, in which products can be generated by composing feature modules. Design by contract is a development methodology, in which methods are specified by annotating them with contracts. Researchers propose to use such contracts to specify feature modules in order to perform different product-line analysis-techniques such as verification and automated detection of feature interactions. We have found six approaches to specify feature modules with contracts in literature. These approaches differ in the way specifications can be refined. Each of them relies on a certain way in which contracts are composed. So far, these contract composition mechanisms must be applied manually for each product. Thus, the evaluation of applications that rely on contracts in feature-oriented programming is laborious, error-prone, or not feasible at all. We formalize the underlying composition mechanism for each existing approach considering possible interpretations, variations, and combinations. Based on our formalization, we provide tool support that can be used to specify feature modules with contracts expressed in the Java Modeling Language. Our tool is integrated into an integrated development environment that provides support for the whole product-line engineering process. Furthermore, it allows the developer to choose the desired contract composition mechanism for each product line. We performed four case studies to evaluate the applicability of different contract composition mechanisms.