Technical Report CS0427

Title: Evaluating Linear-Recursive Logic Queries Against Cyclic Relations
Authors: Eram Gery and Yoav Raz
Abstract: A top-down algorithm is given to evaluate a simple class of recursive logic-queries. The intended scope of the algorithm is linear recursive queries against cyclic relations. A relation defined by a linear recursive rule can be constructed by evaluating successive join expressions generated by rule expansions according to the resolution principle. This naive method was improved by Henschen and Naqvi, and a more efficient method was presented by Banchilon et al. These algorithms use termination condition based on the acyclicity of the base-relations, i.e. they are not applicable if the database may have cyclic-relations. We extend the method for cyclic relations and compare the method to other methods applicable for this domain. The presented algorithm is shown to be advantageous in many cases.
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