Add to ORKGProduct-line architectures present an important approach to increasing software reuse and reducing development cost by sharing an architecture and set of reusable components among a family of products. However, evolution in product-line architectures is more complex than in traditional software development since new, possibly conflicting, requirements originate from the existing products in the product-line and new products that are to be incorporated. In this paper, we present a case study of product-line architecture evolution. Based on the case study, we develop categorizations for the evolution of requirements, the product-line architecture and product-line architecture components. Subsequently, we analyze and present ...