Semantic query optimization for object databases

Abstract

Presents a technique for semantic query optimization (SQO) for object databases. We use the ODMG-93 (Object Data Management Group) standard ODL (Object Database Language) and OQL (Object Query Language) languages. The ODL object schema and the OQL object query are translated into a DATALOG representation. Semantic knowledge about the object model and the particular application is expressed as integrity constraints. This is an extension of the ODMG-93 standard. SQO is performed in the DATALOG representation, and an equivalent logic query and (subsequently) an equivalent OQL object query are obtained. SQO is based on the residue technique of Chakravarthy et al. (1990). We show that our technique generalizes previous research on SQO for object databases. It can be applied to queries with structure constructors and method application. It utilizes integrity constraints about keys, methods and knowledge of access support relations, to produce equivalent queries, which may have more efficient evaluation plans.