Abstract

We present a technique for semantic query optimization (SQO) for object databases. We use the ODMG-93 standard ODL and OQL 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 [3]. 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. 1.

Citations