Database Connectivity Using an Agent-Based Mediator System

This paper describes a technique for creating mediators— information system components that operate among distributed applications and distributed databases. The databases are distributed logically and physically, typically residing on different platforms and having different semantics. A mediator automates the process of merging widely differing databases into a seamless, unified whole to be presented to the user. Our system’s underlying strength is its homogeneity— all components are modeled as Java agents that communicate with each other in a common protocol (KQML) and with a common semantics (the ontology). The mediator-based information system consists of a mediator-reasoning core, a universal ontology, wrappers to align the databases semantically with the ontology, and agents that handle connectivity issues. Each component is modeled as an agent and implemented as a JATLite process. The mediator agent operates as a forward-chaining, rule-based system written declaratively in Jess, the Java Expert System Shell. It is multithreaded to support simultaneous queries and interactions. The mediator’s intelligence is embedded in a fact and rule base residing in a text file that is easily edited. By changing only the rule base, the mediator may be customized for any application.