In an environment in which systems are configured by reusing existing subsystems, the determination of complete and consistent configurations is a non-trivial and error-prone task, although considerable information about the subsystems may already be available from previous configurations. The Configuration Management Assistant is a tool that supports tracking and exploiting such information in the difficult process of re-configuration on a large scale. Its data model was designed to be as independent as possible of configuration management policies and procedures and yet provide substantive assistance in this process. The most important elements of this data model are described in this paper