SEMANTIC QUERY OPTIMIZATION IN RECURSIVE DATABASES.

Semantic query optimization is the process of using semantic knowledge expressed in the form of integrity constraints to transform a query into a semantically equivalent one; one that is thought to be less expensive to process. The authors analyze the possibilities of semantic optimization in a deductive database that includes recursive relations and, consequently, integrity constraints that include recursive literals. They propose a compiled approach to utilizing semantic knowledge in recursive query processing, assuming recursive queries are processed using compiled iterative methods. Also, a method of residue propagation for obtaining implied constraints that are often useful in optimization is presented.