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Certification of Classical Confluence Results for Left-Linear Term Rewrite Systems

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Interactive Theorem Proving (ITP 2016)

Part of the book series: Lecture Notes in Computer Science ((LNTCS,volume 9807))

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Abstract

This paper presents the first formalization of three classic confluence criteria for first-order term rewrite systems by Huet and Toyama. We have formalized proofs, showing that (1) linear strongly closed systems, (2) left-linear parallel closed systems, and (3) left-linear almost parallel closed systems are confluent. The third result is extended to commutation. The proofs were carried out in the proof assistant Isabelle/HOL as part of the library IsaFoR and integrated into the certifier CeTA, significantly increasing the number of certifiable proofs produced by automatic confluence tools.

This work is supported by FWF (Austrian Science Fund) project P27528.

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Notes

  1. 1.

    http://coco.nue.riec.tohoku.ac.jp/.

  2. 2.

    IsaFoR/CeTA and CPF are available at http://cl-informatik.uibk.ac.at/software/ceta/.

  3. 3.

    We do not impose the common variable conditions, i.e., the restriction that \(\ell \) is not a variable and all variables in r are contained in \(\ell \).

  4. 4.

    This bound is necessary to ensure termination of the certifier.

  5. 5.

    http://cops.uibk.ac.at.

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Acknowledgments

We thank Nao Hirokawa for suggesting Lemma 6 and Bertram Felgenhauer and Christian Sternagel for insightful discussion.

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  1. Department of Computer Science, University of Innsbruck, Innsbruck, Austria

    Julian Nagele & Aart Middeldorp

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  1. Julian Nagele
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  2. Aart Middeldorp
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Correspondence to Julian Nagele .

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  1. Inria Nancy – Grand Est, Villers-lès-Nancy, France

    Jasmin Christian Blanchette

  2. Inria Nancy – Grand Est, Villers-lès-Nancy, France

    Stephan Merz

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Nagele, J., Middeldorp, A. (2016). Certification of Classical Confluence Results for Left-Linear Term Rewrite Systems. In: Blanchette, J., Merz, S. (eds) Interactive Theorem Proving. ITP 2016. Lecture Notes in Computer Science(), vol 9807. Springer, Cham. https://doi.org/10.1007/978-3-319-43144-4_18

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  • DOI: https://doi.org/10.1007/978-3-319-43144-4_18

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