Abstract
Constraint Handling Rules (CHR) are a powerful rule based language for specifying constraint solvers. Critical for any rule based language is the notion of confluence, and for terminating CHR programs there is a decidable test for confluence. But many CHR programs that are in practice confluent fail this confluence test. The problem is that the states that illustrate non-confluence are not observable from the initial goals of interest. In this paper we introduce the notion of observable confluence, a more general notion of confluence which takes into account whether states are observable. We devise a test for observable confluence which allows us to verify observable confluence for a range of CHR programs dealing with agents, type systems, and the union-find algorithm.
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Duck, G.J., Stuckey, P.J., Sulzmann, M. (2007). Observable Confluence for Constraint Handling Rules. In: Dahl, V., Niemelä, I. (eds) Logic Programming. ICLP 2007. Lecture Notes in Computer Science, vol 4670. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-540-74610-2_16
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DOI: https://doi.org/10.1007/978-3-540-74610-2_16
Publisher Name: Springer, Berlin, Heidelberg
Print ISBN: 978-3-540-74608-9
Online ISBN: 978-3-540-74610-2
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