Active Object-Relational Mediators

This paper describes an active object-oriented mediator for the enforcement of global consistency between relational legacy databases. We discuss the problem of integrating several local relational systems into a federated system by the usage of an object-oriented mediator system. We explore how relational DBMSs can be enhanced to signal local updates that may violate global constraints without sacri cing too much autonomy and present a database gateway for detection, logging and signalling. We show how the gateway is embedded into the architecture of an object-relational mediator system. We give a solution to the problem of mapping SQL commands to method calls in a C++ based system using a so-called mediator generator. Furthermore, we discuss how the federated system can be enriched by rule mechanisms that make the mediator behave actively.