Large Multidatabases: Beyond Federation and Global Schema Integration

Advances in wide area networking is making the goal of achieving a worldwide interoperable database system closer than ever. Because of the large environment , new problems have surfaced that need to be addressed. We distinguish several reasons for a new design approach. Traditional approaches like global integration and federated approaches are better suited to small and medium scale heterogeneous databases. In a large network of interoperable autonomous heterogeneous databases, the architecture should be exible enough to allow negotiation to take place to establish grouping of databases. In such a large environment, it is important that databases be made aware of other participating databases in an incremental fashion. Further, users should be educated about the space of information in an incremental and dynamic fashion. These goals are to be achieved under the major assumptions that participating databases keep their autonomy intact as much as possible and that the overhead in bridging heterogeneity be proportional to the level of sharing. In this paper, we describe a two-level approach that addresses these issues.