ODMG language extensions for generalized schema versioning support

The management of different schema versions is required inlong-lived database systems to accomplish data structural changes and represent their history. Once a suitable data model for schema versioning support has been defined, appropriate extensions must also be introduced in the data definition and manipulation languages. Such an extension is aimed at making the versioning facilities available at user-interface leveland is the basis for the development of advanced multi-schema applications. In this paper we present extensions to the definition and manipulation language of the standard object-oriented data model ODMG for a generalized schema versioning support. To this end, two versioning modalities will be considered in a single powerful system: temporal versioning and management of alternative design versions. As far as the temporal components are concerned, the proposed extensions of ODL and OQL will be consistent with the TSQL temporal query language