Same Same But Different: Interoperability of Software Product Line Variants

Software Product Lines (SPLs) are an established area of research providing approaches to describe multiple variants of a software product by representing them as a highly variable system. Multi-SPLs (MPLs) are an emerging area of research addressing approaches to describe sets of interdependent, highly variable systems, that are typically managed and developed in a decentralized fashion. Current approaches do not offer a mechanism to manage and orchestrate multiple variants from one product line within the same application.We experienced the need for such a mechanism in an industry project with Deutsche Bahn, where we do not merely model a highly variable system, but a system with highly variable subsystems. Based on MPL concepts and delta-oriented oriented programming, we present a novel solution to the design challenges arising from having to manage and interoperate multiple subsystems with multiple variants: how to reference variants, how to avoid name or type clashes, and how to keep variants interoperable.