Export database derivation in 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 flexible approach to specify the derivation of object-orient ed (OO) export databases from local relational databases. Our export databa se derivation consists of a set of extent derivation structures (EDS) which defines the extent and deep extent of export classes. Having well-defined semantics, the EDS can be readily used in transforming wrapper queries to l ocal queries. Based on the EDS, we developed a wrapper query evaluation str ategy which handles OO queries on the export databases. The strategy is uni que in that it considers the limited query processing capabilities of local database systems as well as the language constraints on the local query la nguages. (C) 1999 Elsevier Science B.V. All rights reserved.