Constraint Management in Loosely Coupled Distributed Databases

Abstract

We provide a framework for managing integrity constraints that span multiple databases in loosely coupled, heterogeneous environments. Our framework enables the formal description of (1) interfaces provided by a database for the data items involved in multi-database constraints; (2) strategies for monitoring and maintaining multi-database constraints; (3) guarantees regarding the consistency of multi-database constraints. With our approach one can define "relaxed" constraints that only hold at certain times or under certain conditions. Such constraints appear often in practice and cannot be handled effectively by conventional, transaction-based approaches. We also describe a toolkit, based on our framework, for enforcing constraints over heterogeneous systems. The toolkit includes a general-purpose, distributed constraint manager that can be easily configured to a given environment and constraints. A first version of the toolkit has been implemented and is under evaluation.