Architectural Evolution of Legacy Product Families

Recent research has focused on the concept of product family architecture. We address the more specific case of legacy product families, whose life spans across several years and product generations.We illustrate the method we use to describe legacy product family architecture and manage its evolution. To describe of the family architecture we use two separate documents. The reference architecture, which describes the abstract architecture that is instantiated in every product, and contains architecturally significant rules for adding new components to the system. And the configuration architecture, which maps the product family features into the various products, thus, allowing to model commonality and variability.The concept of a family is an abstraction that automatically generates a new layer in every product. This layer includes all the software that is common to other products in the family, and is, naturally, less prone to change than the layer constituted by software which is specific to the product.In certain domains like mobile telecommunications, when new products are added to the family, they tend to share most of the stable features that belong to legacy products. This phenomenon abstracts the issues of architectural evolution from the single products to the entire family scope.We also sketch the process we follow to maintain the documents that model the product family architecture. Our approach combines reverse and forward architecting activities, and is currently applied in Nokia Mobile Phones. Research on the issues of architectural modelling is still insufficient: we propose some hints for future work.