Intrinsic Support for Metadata Integration in Relation Federations

This paper investigates the idea of supporting metadata querying and restructuring using extensions of the SQL:1999 facilities for integrity constraints and active databases. Our approach involves associating meta-functionality with federation relations by means of constraints, assertions, and triggers. This approach can underpin recent work on dynamic interoperability in relational federations involving an extended relational model. An advantage of the approach described here is that it provides intrinsic, database-driven support for dynamic restructuring and federated interoperability. A drawback is that, if not developed properly, the extended notions of constraints, assertions, and triggers can exacerbate existing issues with the practical efficiency of database-driven integrity support. We discuss this trade-off, and conclude with a brief indication of how our work fits in to existing work and some directions for future work.