This paper focuses on the version models underlying both commercial systems and research prototypes. It provides an overview and classification of different versioning paradigms. Furthermore, it defines and relates fundamental concepts such as revisions, variants, configurations, and changes. In particular, we focus on intensional versioning, i.e., construction of versions based on configuration rules. Finally,we provide an overview of systems whichhave had significant impact on the development of the SCM discipline, and classify them according to a detailed taxonomy

Distributed con guration management is intended to support the activities of projects that span multiple sites. NUCM is a testbed that we are developing to help us explore the issues of distributed con guration management. NUCM separates con guration management repositories (i.e., the stores for versions of artifacts) from con guration management policies (i.e., the procedures by which the versions are manipulated) by providing a generic model of a distributed repository and an associated programmatic interface. This paper describes the model and the interface, presents an initial repository distribution mechanism, and sketches how NUCM can be used to implement two, rather di erent, con guration management policies, namely checkin/check-out and change sets.