Software maintenance and evolution are among the most challenging and cost-intensive activities in software engineering. This is not different for software product lines due to their complexity and long life-span. New customer requirements, technology changes and internal enhancements lead to the continuous evolution of a product line's reusable assets. Due to the size of product lines, single stakeholders or teams can only maintain a small part of a system which poses additional challenges for evolution. This paper presents an approach supporting product line evolution by organizing variability models of large-scale product lines as a set of interrelated model fragments defining the variability of particular parts of the system. The approach allows semi-automatic merging of fragments into complete variability models. We also provide tool support to automatically detect changes that would make models and the architecture inconsistent. Furthermore, our approach supports the co-evolution of variability models and their respective meta-models. We illustrate the approach with examples from an ongoing industry collaboration.

Evolution is a permanent challenge in product line engineering. Reusable assets such as software components or documents evolve continuously due to new customer requirements or technology changes. This leads to modifications or extensions of the product line's variability models describing the reference architecture. Due to the large size of product lines, single stakeholders or teams can only maintain a small part of a system which poses additional challenges for evolution. This paper presents a tool-supported approach for building and maintaining variability models of large-scale product lines. We structure variability models into multiple model fragments of manageable size that can be created and maintained by individual teams. Model fragments can be merged semi- automatically into a variability model. We illustrate the approach with examples from ongoing industry collaboration.

Product line engineering comprises many heterogeneous activities such as capturing the variability of reusable assets, supporting the derivation of products from the product line, evolving the product line, or tailoring the approach to the specifics of a domain. The inherent complexity of product lines implicates that tool support is inevitable to facilitate smooth performance and to avoid costly errors. Product line engineering tools have to support heterogeneous stakeholders involved in diverse activities. Tool integration therefore is of particular importance to foster their seamless cooperation. However, the integration is difficult to achieve due to the diversity of models and work products. This paper describes the DOPLER tool suite which has been developed to provide such integrated support. The tool suite is flexible and extensible to support domain-specific needs