Export Database Derivation and Query Processing for Object-Oriented Wrappers

Wrappers export the schema and data of existing heterogeneous databases and support queries on them. In the context of cooperative information systems, we present a exible approach to specify the derivation of object-oriented export databases from local relational databases. Our export database derivation consists of a set of extent derivation structures which de-nes the extent and deep extent of export classes. Having well-deened semantics, the extent derivation structures can be readily used in transforming wrapper queries to local queries. Based on the extent derivation structures, we developed a wrapper query evaluation strategy which handles object-oriented queries on the export databases. The strategy further considers the limited query processing capabilities of local database systems and the language constraints on the local query languages.