Many large corporations find themselves with a massive legacy database problem. Their data is distributed across many semantically related databases that are physically and logically disjoint. Until now, there have been two primary approaches for interconnecting heterogeneous database systems: (a) point solutions, in which software systems supporting focused interconnections between databases are constructed on an as-needed and ad hoc basis; and (b) global solutions, in which a common, logical database is created that encompasses a very large number of databases. (A variation of the latter is the federated approach, which involves a global federation manager that controls all interaction between the component databases.) The Diplomat project chooses a middle ground between these two extremes, and provides technology to support multiple loose database interconnections called `alliances`. The framework also provides mechanisms to enforce consistency between individual databases, and across alliances. The project draws on existing research on view specification, inter-database constraints, and information flow. This research serves as a proof of concept that maintainers of large business applications (such as banking, insurance, and telecommunications) can integrate multiple, heterogeneous, legacy database systems in a cost-effective, evolvable fashion.
