Federated Schemata in ODMG

Due to the increasing acceptance of database management systems, many enterprises store most of their information in such databases. Unfortu­ nately, the diversity of database management systems frequently leads to the situation, that different units of an enterprise use different systems or at least incompatible schemata, which makes it very burdensome to exchange data between these units. To increase efficiency of these exist­ ing databases, and to feed new applications in a homogenized fashion, it is getting more and more necessary to make the databases interoper­ able and to provide a unified access to them. This paper describes an approach to introduce the notion of virtual classes into the evolving ob­ ject database standard ODMG-93. These virtual classes can be used to establish a federation database which is capable of importing and export­ ing data from and to other databases, to integrate (or just to provide in parallel) information from different data bases, and to tailor the overall· schema for specific applications.