Integrating databases with publish/subscribe

Publish/subscribe is emerging as an appropriate communication paradigm for large-scale, widely-distributed systems. In this paper, we describe our work on integrating active databases with publish/subscribe, using PostgreSQL and Hermes as the experimental context. In the proposed architecture, each database manager defines and advertises change events, in contrast with a continuous query model. Advertised events, which may span a number of physical relations, correspond to the virtual relations of a security view. Clients subscribe to events of interest, and can refine their subscriptions through content-based filter expressions. An event is published whenever a database change, detected via a dynamic triggering layer, matches some active subscription. Security and routing of database events are handled in the same way as for conventional Hermes events.