Exploiting object technology to support product variability

A key promise of object oriented technology is improved change containment. One application of this quality is to increase reuse by supporting product variations within a software product line. This is the focus of a Boeing effort to apply the product line software approach to the tactical aircraft mission processing domain. Another is to ease evolution during maintenance of a single product. The common goal is to facilitate anticipated variability between different software versions. Richly expressive languages like C++ and Ada95 offer many techniques to control and support variability, including inheritance, aggregation, generic programming, and conditional compilation. The breadth of alternatives available requires that developers understand the relative merit of each in different situations, This paper focuses not on the features themselves, but on guiding their optimal selection and application by discussing how well different language features support different variation types.