On global query optimization in multidatabase systems

Multidatabase management systems (MDBMS) enable data sharing among heterogeneous local databases (component databases) and thus provide interoperability required by diverse applications. In multidatabase systems, user requests data from the multidatabase by posing non-procedural queries. For a query involving more than one database, a global optimization should be performed to achieve good overall system performance. Among the research topics in multidatabase systems, little is reported on global query optimization. One of the reasons is that the significant differences among the optimization problem for multidatabase and the distributed homogeneous system are not well recognized