Maintenance and Mediation in Database Federations

This paper proposes a novel approach to the processing of global queries in a tight federation of heterogeneous relational databases. It is based on query correspondence assertions, which are declarative rules that describe semantic correspondences between different relational schemas. A mediator uses these rules to translate queries against the federated schema into semantically contained sequences of queries against source databases. We argue that this approach has significant maintenance advantages over traditional approaches.