Operational semantics and confluence of constraint propagation rules

  • Slim Abdennadher
Session 5a
Part of the Lecture Notes in Computer Science book series (LNCS, volume 1330)


Constraint Handling Rules (CHR) allow one to specify and implement both propagation and simplification for user-defined constraints. Since a propagation rule is applicable again and again, we present in this paper for the first time an operational semantics for CHR that avoids the termination problem with propagation rules.

In previous work [AFM96], a sufficient and necessary condition for the confluence of terminating simplification rules was given inspired by results about conditional term rewriting systems. Confluence ensures that the solver will always compute the same result for a given set of constraints independent of which rules are applied. The confluence of propagation rules was an open problem. This paper shows that we can also give a sufficient and a necessary condition for confluence of terminating CHR programs with propagation rules based on the more refined operational semantics.


Operational Semantic Critical Pair Constraint Solver Minimal Pair Applicability Condition 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag Berlin Heidelberg 1997

Authors and Affiliations

  • Slim Abdennadher
    • 1
  1. 1.Computer Science DepartmentUniversity of MunichMünchenGermany

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