The paper describes an active abject-oriented mediator for theenforcement of global consistency between relational legacy databases.The authors discuss the problem of integrating several local relationalsystems into a federated system by the usage of an object-orientedmediator system. They explore how relational DBMSs can be enhanced tosignal local updates that may violate global constraints withoutsacrificing too much autonomy and present a database gateway fordetection, logging and signalling. They show how the gateway is embeddedinto the architecture of an object-relational mediator system. They givea solution to the problem of mapping SQL commands to method calls in aC++ based system using a so-called mediator generator. Furthermore, theydiscuss how the federated system can be enriched by rule mechanisms thatmake the mediator behave actively
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