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<p>The authors describe a scheme to utilize semantic knowledge in optimizing a user-specified query. The semantics is represented as function-free clauses in predicate logic. The scheme uses a graph-theoretic approach to identify redundant joins and restrictions present in a given query while adding additional profitable specifications to it. Dynamic and heuristic interaction of three entities-schema, semantics, and query-forms the basis of the algorithm. The implementation architecture of the algorithm and test results on a representative set of data are presented. Issues associated with updating of semantic constraints are addressed, and an algorithm for semantic maintenance is introduced.</p>
semantic query optimizer; semantic knowledge; user-specified query; function-free clauses; predicate logic; graph-theoretic approach; redundant joins; schema; semantics; semantic maintenance; graph theory; optimisation; relational databases

Z. Ozsoyoglu and S. Shenoy, "Design and Implementation of a Semantic Query Optimizer," in IEEE Transactions on Knowledge & Data Engineering, vol. 1, no. , pp. 344-361, 1989.
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