Conference Paper

A Comparison of Constraint Handling Rules with Equivalent Transformation Rules.

Conference: Proceedings of the International Conference on Modeling, Simulation & Visualization Methods, MSV '04 & Proceedings of the International Conference on Algorithmic Mathematics & Computer Science, AMCS '04, June 21-24, 2004, Las Vegas, Nevada, USA
Source: DBLP


We have proposed a novel computation framework called Equivalent Transformation (ET). The ET frame- work is a rewriting system in which computation is exe- cuted by rewriting rules. Rewriting rules of the ET frame- work are called Equivalent Transformation Rules (ETRs). The theory of ET guarantees the correctness of the com- putation by ETRs. Multi-head ETRs which have multiple atoms in their head part are valid ETRs. Constraint Handling Rules (CHR) are declarative lan- guage extension designed for writing user-defined con- straints. CHR allows to use multi-head guarded rules for its computation. This paper compares the rewriting rules of ET and CHR, especially multi-head rules. We show that all CHR rules can be simply transformed into correct ETRs preserving their logical meanings. Examples of the correct ETRs which can not be represented as CHR rules are also given. Therefore CHR rules can be regarded as proper subclass of ETRs.

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