Consistency control of replicated data in federated databases

The effective use of distributed databases requires a proper balance between autonomy and coordination. A critical decision influencing the autonomy of local sites concerns the method for update propagation to replicated data. An identity connection model is designed to specify replication, permissible delay in the consistency of copies, and data derivation rules. This model allows the nature of the coupling between autonomous sites in a distributed database to be declared. A transaction processing mechanism is under development for consistency control of replicated data based on the identity connection model. The mechanism unifies existing approaches to update propagation, and it supports the filtering of update transactions that cannot meet consistency requirements as well as the alerting of query transactions that cannot see consistent data