Set-Term Matching in a Logic Database Language

Existing set-term matching algorithms [l] for logic-based database languages, of which set terms have the commutative and idempotent properties, have several problems: Given a pair of set terms, matchers can only be computed uequentiollyand duplicatedmatchers are generated. Hence, these algorithms cannot take the advantage of existing multiple processors for computing all matchers in parallel. Further, duplicated matchers are redundant and undesirable. In order to overcome these shortcomings, we propose an improved set-term matching approach for LDL/NR, a logic database language for nested relations, which generates non-redundant matchers for a given pair of set terms in parallel. The approach thus solves the sequential and redundant problems in [I].