Abstract
Since relational DBMSs are widespreadproviding a relational global view for users who are only familiar with the relational model to access data in a multidatabase system is signicant In this paperwe propose an approach to integrate database schemas into a relational global view which consists of concept hierarchies A concept hierarchy is composed of relation schemes with the same conceptto which specialization and generalization can be specied to enrich the semantics of the relational view Based on the concept hierarchiesa procedure is designed to decompose a global query to local subqueries and a set of transformation rules are developed to transform a query into an equivalent one for query optimization Int