Flexible Integration and Derivation of Heterogeneous Schemata in Federated Database Systems 1

In this report concepts for the process of schema integration and transformation in Federated Database Systems (FDBS) are suggested, which are exible in the integration of local and in the derivation of external schemata. An FDBS has to support diierent data models of local database systems. Furthermore, it has to ooer a means to derive external schemata, which can diier in their underlying data models and in the way of representing the federated data according to speciic views of global applications. In order to move local applications from their local schemata to external schemata above the federation layer, these schemata must no be diierent. Concepts to derive such external schemata are introduced. In addition to this, applying the suggested concepts, the process of integration and transformation can be done in a methodological manner. In this report, the use of a semantically poor data model as the canonical data model and a two-phase-restructuring process for the schema integration and transformation are motivated. These concepts are important steps to t the requirements above. Acknowledgements Thanks to Gunter Saake, Michael HH oding and Can T urker for many creative discussions. I also have beneeted from linguistic advice provided by Victoria Forrest-Hampson, Mark Krogel and Can T urker.