Product-line requirements specification (PRS): an approach and case study

Software product-line engineering can provide significant gains in quality and productivity through systematic reuse of software´s conceptual structures. For embedded safety- or mission-critical systems, much of the development effort goes into understanding, specifying, and validating the requirements. If developers can reuse rather than re-do requirements for families of similar systems, we can improve productivity while significantly reducing the opportunity for requirements errors. The paper describes a systematic approach to developing a Product-line Requirements Specification (PRS) for such systems. The PRS explicitly represents the family´s common requirements as well as the allowed variations that distinguish family members. When completed, the PRS definition also supports generation of well-formed software requirements specifications (SRS) for members of the product line. We describe a process for developing a PRS starting from an analysis of a program family´s commonalities and variabilities. The approach is illustrated with examples from a case study of a real family of systems, the Rockwell Collins Commercial Flight Control System product-line