Implementing Software Product Lines using Traits

A software product line (SPL) is a set of software systems with well-defined commonalities and variabilities that are developed by managed reuse of common artifacts. In this paper, we present a novel approach to implement SPL by fine-grained reuse mechanisms which are orthogonal to class-based inheritance. We introduce the Featherweight Record Trait Java (FRTJ) calculus where units of product functionality are modeled by traits, a construct that was already shown useful with respect to code reuse, and by records, a construct that complements traits to model the variability of the state part of products explicitly. Records and traits are assembled in classes that are used to build products. This composition of product functionalities is realized by explicit operators of the calculus, allowing code manipulations for modeling product variability. The FRTJ type system ensures that the products in the SPL are type-safe.