An active approach to constraint maintenance in a multidatabase environment

Methods for the expression and maintenance of integrity constraints have always been an important issue in database systems research. This research presents an active approach for integrity constraint maintenance in a multidatabase, where constraints that exist between heterogeneous database sources can be expressed in a high-level declarative Multidatabase Constraint Specification Language (MCSL). MCSL supports the expression of disjoint constraints, reference constraints, general existence constraints, and aggregation constraints between multiple data sources. Current research on active databases has been extended to develop a distributed active rule language (DARL) for MCSL constraints. DARL rules for maintaining interdatabase constraints are automatically generated from an internal, logical representation of MCSL constraints. During the rule generation process, constraint analysis techniques are used to analyze the effects that database operations have on constraints. Semantic information about distributed components in the rule generation process is also used to minimize remote database access. Since writing distributed active rules is a complex and error prone task, the algorithms presented in this research allow the automatic generation of rules for constraints defined over multidatabase environments. The algorithms for generating DARL rules from MCSL constraints have been implemented and a distributed architecture for the execution of DARL rules has been designed and prototyped in support of this research. The results presented in this dissertation advance constraint specification and maintenance techniques for multidatabase systems by providing a high-level language for the expression of non-trivial constraints, together with a rule language, rule generation techniques, and an execution environment for distributed constraint maintenance.