A proof theory of (omega-)context-free languages, via non-wellfounded proofs

Fuente: arXiv
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Auteurs principaux: Das, Anupam, De, Abhishek
Format: Preprint
Publié: 2024
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author Das, Anupam
De, Abhishek
author_facet Das, Anupam
De, Abhishek
contents We investigate the proof theory of regular expressions with fixed points, construed as a notation for (omega-)context-free grammars. Starting with a hypersequential system for regular expressions due to Das and Pous, we define its extension by least fixed points and prove soundness and completeness of its non-wellfounded proofs for the standard language model. From here we apply proof-theoretic techniques to recover an infinitary axiomatisation of the resulting equational theory, complete for inclusions of context-free languages. Finally, we extend our syntax by greatest fixed points, now computing omega-context-free languages. We show the soundness and completeness of the corresponding system using a mixture of proof-theoretic and game-theoretic techniques.
format Preprint
id arxiv_https___arxiv_org_abs_2404_16231
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle A proof theory of (omega-)context-free languages, via non-wellfounded proofs
Das, Anupam
De, Abhishek
Logic in Computer Science
Logic
We investigate the proof theory of regular expressions with fixed points, construed as a notation for (omega-)context-free grammars. Starting with a hypersequential system for regular expressions due to Das and Pous, we define its extension by least fixed points and prove soundness and completeness of its non-wellfounded proofs for the standard language model. From here we apply proof-theoretic techniques to recover an infinitary axiomatisation of the resulting equational theory, complete for inclusions of context-free languages. Finally, we extend our syntax by greatest fixed points, now computing omega-context-free languages. We show the soundness and completeness of the corresponding system using a mixture of proof-theoretic and game-theoretic techniques.
title A proof theory of (omega-)context-free languages, via non-wellfounded proofs
topic Logic in Computer Science
Logic
url https://arxiv.org/abs/2404.16231