Feature diagrams: A survey and a formal semantics

Feature Diagrams (FD) are a family of popular modelling languages usedfor engineering requirements in software product lines. FD were first introduced by Kang as part of the FODA (Feature Oriented Domain Analysis) method back in 1990. Since then, various extensions of FODA FD were devised to compensate for a purported ambiguily and lack of precision and expressiveness. However, they never received a proper formal semantics, which is the hallmark of precision and unambiguity as well as a prerequisite for efficient and safe tool automation. In this paper we first survey FD variants. Subsequently, we generalize the various syntaxes through a generic construction called Free Feature Diagrams (FFD). Formal semantics is defined at the FFD level, which provides unambiguous definition for all the surveyed FD variants in one shot. Allformalization choicesfound a clear answer in the original FODA FD definition, which proved that although informal and scattered throughout many pages, it suffered no ambiguity problem. Our definition has several additional advantages: it is formal, concise and generic. We thus argue that it contributes to improve the definition, understanding, comparison and reliable implementation of FD languages.