Towards understanding requirement evolution in a software product line an industrial case study

In most software development practices, software requirements and architecture are addressed simultaneously. The architecture may grow based on a core specification of requirements, and the requirements may also be elicited incrementally as the architecture gets more and more concrete. In this paper, we present a case study on the development history of Wingsoft Examination System Product Line (WES-PL), an active, industrial software product line with a history of more than eight years. We focus on 10 member products, 51 major versions that have been delivered to customer or archived in the repository between December 2003 and May 2012, by tracing both requirement and architectural changes. We identify a requirement change classification from the viewpoint of architectural impact. We claim that software requirements are negotiated and may be guided by existing software architecture design, especially in the process of software product line development. Product strategy requirements play an important role in marketing requirement negotiation. We also find typical evidences showing that a product leader or architect has to make difficult decisions to keep a balance between marketing requirements from customer-side and software architectural design from his own side.