Equational Reasoning Modulo Commutativity in Languages with Binders (Extended Version)

Fuente: arXiv
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Autores principales: Caires-Santos, Ali K., Fernández, Maribel, Nantes-Sobrinho, Daniele
Formato: Preprint
Publicado: 2025
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author Caires-Santos, Ali K.
Fernández, Maribel
Nantes-Sobrinho, Daniele
author_facet Caires-Santos, Ali K.
Fernández, Maribel
Nantes-Sobrinho, Daniele
contents Many formal languages include binders as well as operators that satisfy equational axioms, such as commutativity. Here we consider the nominal language, a general formal framework which provides support for the representation of binders, freshness conditions and $α$-renaming. Rather than relying on the usual freshness constraints, we introduce a nominal algebra which employs permutation fixed-point constraints in $α$-equivalence judgements, seamlessly integrating commutativity into the reasoning process. We establish its proof-theoretical properties and provide a sound and complete semantics in the setting of nominal sets. Additionally, we propose a novel algorithm for nominal unification modulo commutativity, which we prove terminating and correct. By leveraging fixed-point constraints, our approach ensures a finitary unification theory, unlike standard methods relying on freshness constraints. This framework offers a robust foundation for structural induction and recursion over syntax with binders and commutative operators, enabling reasoning in settings such as first-order logic and the $π$-calculus.
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id arxiv_https___arxiv_org_abs_2502_19287
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Equational Reasoning Modulo Commutativity in Languages with Binders (Extended Version)
Caires-Santos, Ali K.
Fernández, Maribel
Nantes-Sobrinho, Daniele
Logic in Computer Science
Many formal languages include binders as well as operators that satisfy equational axioms, such as commutativity. Here we consider the nominal language, a general formal framework which provides support for the representation of binders, freshness conditions and $α$-renaming. Rather than relying on the usual freshness constraints, we introduce a nominal algebra which employs permutation fixed-point constraints in $α$-equivalence judgements, seamlessly integrating commutativity into the reasoning process. We establish its proof-theoretical properties and provide a sound and complete semantics in the setting of nominal sets. Additionally, we propose a novel algorithm for nominal unification modulo commutativity, which we prove terminating and correct. By leveraging fixed-point constraints, our approach ensures a finitary unification theory, unlike standard methods relying on freshness constraints. This framework offers a robust foundation for structural induction and recursion over syntax with binders and commutative operators, enabling reasoning in settings such as first-order logic and the $π$-calculus.
title Equational Reasoning Modulo Commutativity in Languages with Binders (Extended Version)
topic Logic in Computer Science
url https://arxiv.org/abs/2502.19287