Configuration management with version sets: a unified software versioning model and its applications

Software configuration management (SCM) is the discipline for organizing and controlling evolving complex software systems. Several SCM tools and systems exist that automate and integrate SCM tasks like version identification, system modeling, product construction, or team work coordination. However, the choice of an SCM system is still a long-term commitment: Each SCM system comes with its own SCM policy, which is often centered on a specific environment and thus seldom interoperates, yet alone integrates with other SCM tools. This is unfortunate, as the entire software development process must be adapted to fit the system’s SCM policy. We want SCM systems that adapt to their users, rather than vice versa. As a foundation, we propose a unified versioning model, the version set model. Version sets denote versions, components, and configurations by feature terms, that is, boolean terms over (feature:value)-attributions. Through feature logic, a wellestablished formalism for knowledge representation and logic programming, we define the semantics of SCM tasks and concepts. Our results are as follows: Unified versioning. Version sets provide one single formalism to express all versioning dimensions as well as constraints on them, integrating SCM concepts like revisions, variants, workspaces, and configurations in one single model. The SCM policy is not constrained by decisions made in lower SCM layers. Integration of changes and revisions. Configuration constraints, expressed in feature logic, allow us to capture the entire range of temporal versioning— from the rigidness of versions-oriented models to the flexibility of changeoriented models. Consistency checking under ambiguity. Through feature logic, we deduce the features and the consistency of configurations as well as derived compo-