The success of very large product lines systems with
globally distributed stakeholders often builds significantly on the implicit knowledge of individuals. Final products are typically built by integrating numerous detailed specifications of subsystems. But how exactly all these parts can and need to be integrated to build valid end products is often left unspecified and to numerous discussions, reviews and the expertise of senior architects and product managers.
Building a high-level product line requirements model that explicitly and formally specifies common and variable requirements, their precise integration semantics and the constraints for selecting variable features helps significantly to manage this crucial and often tacit requirements knowledge. Based on an industrial exemplar we motivate and demonstrate such an approach and discuss our early ﬁndings regarding knowledge and rationale management in product line requirements engineering.