The interaction and coordination of Expert systems and Databases is a topic which is receiving tremendous attention. Database management systems and Expert systems knowledge representation formalisms evolved as solutions to apparently quite different problems. Recent trends have shown, however, many present and future computer applications could benefit from an effective and efficient marriage of these two technologies. As Expert systems are becoming increasingly complex and diverse, efficient management of their growing knowledge bases is required. Moreover, with the widespread use of Database management systems, the operational data required by the Expert systems is often already available from an online databse. Therefore a number of interface methodologies and prototypes are developed, but their function is limited; only data transfer from Database to Expert system. Our major interest, in this thesis, is the development of more efficient and practical coordinating methodology between multiple Expert systems and a Relational DBMS. But, unfortunately our approach is also dependent on specific domain. So the application scenario is presented first. Then we provide the coordination methodology which sustains consistency with the minimum maintenance effort under decentralized data management environment, controls the relationships among Expert systems and coordinates bi-directional data flow. The prototype is developed according to this methodology using the Expert system development tool UNIK and LISP language.