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Extending ODMG for federated database systems

A federated database system (FDBS) allows uniform and transparent access to the data of multiple heterogeneous DBS. Therefore the federation layer converts the heterogeneous data into a canonical data model. Object-oriented data models are shown to be most appropriate for a canonical data model. As a new standard has arisen in the object-oriented database area, ODMG-93 (ODMG), the paper extends the interfaces of ODMG (with C++ binding) for an FDBS. The author extends the syntax of the ODMG object definition language (ODL) to a schema integration language. It allows to derive federated schemata from existing DBS schemata. The syntax of the object manipulation language (OML) and object query language (OQL) do not have to be extended for an FDBS but can directly serve as a global interface. Only the semantics needs to be extended in the sense that cell operations allow transparent data access on multiple heterogeneous DBS.