Representing and Composing First-class Features with FeatureJ

Software product lines (SPLs) enable creating product families, set of products that differ in terms of features. Traditionally, techniques for implementing features have sided with one of the two views of features: as distinguishable characteristics or as increments/changes in program functionality of the software under consideration. We argue that in order to realize the full potential of features as a separation of concerns mechanism or a modularity mechanism in its own right, both of these views must be supported by the representation of features. Furthermore, the composition of such uniformly represented features should be streamlined so that both can evolve together. Towards this end, we present FeatureJ, an implementation technique that integrates features, variants, and product lines as first-class entities, namely types, in the Java programming language. We review the trends in the representation and composition of features in the current implementation techniques and arrive at a set of requirements to represent features as first-class entities. We demonstrate the syntax of FeatureJ and explain its compiler architecture with a running example of a product line. We compare our implementation approach with other approaches in terms of the representation and composition of features and state the advantages that our approach brings to the implementation of SPLs.