An object-oriented framework for managing cooperating legacy databases

We describe a general semantic framework for precise specification of so-called database federations. A database federation provides for tight coupling of a collection of heterogeneous legacy databases into a global integrated system. Our approach to database federation is based on the UML/OCL data model, and aims at the integration of the underlying database schemas of the component legacy systems to a separate, newly defined integrated database schema. Our approach to coupling of component databases into a global, integrated system is based on mediation. Our major result is that mediation in combination with a so-called integration isomorphism integrates component schemas without loss of constraint information; i.e., constraint information available at the component level. remains intact after integration on the level of the virtual federated, database. Our approach to integration also allows for specification of additional inter-database constraints between the component databases.