A proof theory of right-linear (omega-)grammars via cyclic proofs (2401.13382v1)
Abstract: Right-linear (or left-linear) grammars are a well-known class of context-free grammars computing just the regular languages. They may naturally be written as expressions with (least) fixed points but with products restricted to letters as left arguments, giving an alternative to the syntax of regular expressions. In this work, we investigate the resulting logical theory of this syntax. Namely, we propose a theory of right-linear algebras (RLA) over of this syntax and a cyclic proof system CRLA for reasoning about them. We show that CRLA is sound and complete for the intended model of regular languages. From here we recover the same completeness result for RLA by extracting inductive invariants from cyclic proofs, rendering the model of regular languages the free right-linear algebra. Finally, we extend system CRLA by greatest fixed points, nuCRLA, naturally modelled by languages of omega-words thanks to right-linearity. We show a similar soundness and completeness result of (the guarded fragment of) nuCRLA for the model of omega-regular languages, employing game theoretic techniques.
- The theory of parsing, translation, and compiling. Prentice-Hall, Inc., USA, 1972.
- Hans Bekić. Definable operations in general algebras, and the theory of automata and flowcharts, pages 30–55. Springer Berlin Heidelberg, Berlin, Heidelberg, 1984.
- Wojciech Buszkowski. On Action Logic: Equational Theories of Action Algebras. Journal of Logic and Computation, 17(1):199–217, 10 2006.
- Theory of ω𝜔\omegaitalic_ω-languagesi, ii: Characterizations of ω𝜔\omegaitalic_ω-context-free languages. Journal of Computer and System Sciences, 15(2):169–208, 1977.
- Completeness results for omega-regular algebras. Journal of Logical and Algebraic Methods in Programming, 84(3):402–425, 2015. 13th International Conference on Relational and Algebraic Methods in Computer Science (RAMiCS 2012).
- Ernie Cohen. Separation and reduction. In Roland Backhouse and José Nuno Oliveira, editors, Mathematics of Program Construction, pages 45–59, Berlin, Heidelberg, 2000. Springer Berlin Heidelberg.
- John H. Conway. Regular algebra and finite machines. Chapman and Hall mathematics series. Chapman and Hall, 1971.
- Left-handed completeness for kleene algebra, via cyclic proofs. In Gilles Barthe, Geoff Sutcliffe, and Margus Veanes, editors, LPAR-22. 22nd International Conference on Logic for Programming, Artificial Intelligence and Reasoning, volume 57 of EPiC Series in Computing, pages 271–289. EasyChair, 2018.
- Comparing Infinitary Systems for Linear Logic with Fixed Points. In Patricia Bouyer and Srikanth Srinivasan, editors, 43rd IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2023), volume 284 of Leibniz International Proceedings in Informatics (LIPIcs), pages 40:1–40:17, Dagstuhl, Germany, 2023. Schloss Dagstuhl – Leibniz-Zentrum für Informatik.
- A cut-free cyclic proof system for Kleene algebra, September 2017. Preprint. https://hal.science/hal-01558132.
- A cut-free cyclic proof system for kleene algebra. In Renate A. Schmidt and Cláudia Nalon, editors, Automated Reasoning with Analytic Tableaux and Related Methods - 26th International Conference, TABLEAUX 2017, Brasília, Brazil, September 25-28, 2017, Proceedings, volume 10501 of Lecture Notes in Computer Science, pages 261–277. Springer, 2017.
- Non-Wellfounded Proof Theory For (Kleene+Action)(Algebras+Lattices). In Dan R. Ghica and Achim Jung, editors, 27th EACSL Annual Conference on Computer Science Logic (CSL 2018), volume 119 of Leibniz International Proceedings in Informatics (LIPIcs), pages 19:1–19:18, Dagstuhl, Germany, 2018. Schloss Dagstuhl – Leibniz-Zentrum für Informatik.
- Intuitionistic gödel-löb logic, à la simpson: labelled systems and birelational semantics. CoRR, abs/2309.00532, 2023. Accepted to CSL ’24.
- Algebraically complete semirings and greibach normal form. Annals of Pure and Applied Logic, 133(1):173–203, 2005. Festschrift on the occasion of Helmut Schwichtenberg’s 60th birthday.
- Infinitary axiomatization of the equational theory of context-free languages. Electronic Proceedings in Theoretical Computer Science, 126:44–55, August 2013.
- Dick Grune and Ceriel J. H. Jacobs. Regular Grammars and Finite-State Automata, pages 137–164. Springer New York, New York, NY, 2008.
- Cyclic proofs for transfinite expressions. In Florin Manea and Alex Simpson, editors, 30th EACSL Annual Conference on Computer Science Logic, CSL 2022, February 14-19, 2022, Göttingen, Germany (Virtual Conference), volume 216 of LIPIcs, pages 23:1–23:18. Schloss Dagstuhl - Leibniz-Zentrum für Informatik, 2022.
- Concurrent kleene algebra. In Mario Bravetti and Gianluigi Zavattaro, editors, CONCUR 2009 - Concurrency Theory, pages 399–414, Berlin, Heidelberg, 2009. Springer Berlin Heidelberg.
- Peter Jipsen. From semirings to residuated kleene lattices. Studia Logica, 76:291–303, 03 2004.
- Ll-regular grammars. Information Processing Letters, 4(2):31–37, 1975.
- S. C. Kleene. Representation of Events in Nerve Nets and Finite Automata, pages 3–42. Princeton University Press, Princeton, 1956.
- D. Kozen. A completeness theorem for kleene algebras and the algebra of regular events. Information and Computation, 110(2):366–390, 1994.
- Dexter Kozen. On action algebras. Logic and Information Flow, pages 78–88, 1994.
- Dexter Kozen. Kleene algebra with tests. ACM Trans. Program. Lang. Syst., 19(3):427–443, may 1997.
- Dexter Kozen. On hoare logic and kleene algebra with tests. ACM Trans. Comput. Logic, 1(1):60–76, jul 2000.
- Daniel KROB. A complete system of b-rational identities. In Michael S. Paterson, editor, Automata, Languages and Programming, pages 60–73, Berlin, Heidelberg, 1990. Springer Berlin Heidelberg.
- Kleene algebra with tests: Completeness and decidability. In Dirk van Dalen and Marc Bezem, editors, Computer Science Logic, pages 244–259, Berlin, Heidelberg, 1997. Springer Berlin Heidelberg.
- Left-handed completeness. In Wolfram Kahl and Timothy G. Griffin, editors, Relational and Algebraic Methods in Computer Science, pages 162–178, Berlin, Heidelberg, 2012. Springer Berlin Heidelberg.
- Left-handed completeness. Theoretical Computer Science, 807:220–233, 2020. In memory of Maurice Nivat, a founding father of Theoretical Computer Science - Part II.
- Haas Leiß. Towards kleene algebra with recursion. In Egon Börger, Gerhard Jäger, Hans Kleine Büning, and Michael M. Richter, editors, Computer Science Logic, pages 242–256, Berlin, Heidelberg, 1992. Springer Berlin Heidelberg.
- Hans Leiss. The Matrix Ring of a mu-Continuous Chomsky Algebra is mu-Continuous. In Jean-Marc Talbot and Laurent Regnier, editors, 25th EACSL Annual Conference on Computer Science Logic (CSL 2016), volume 62 of Leibniz International Proceedings in Informatics (LIPIcs), pages 6:1–6:15, Dagstuhl, Germany, 2016. Schloss Dagstuhl – Leibniz-Zentrum für Informatik.
- Matti Linna. On ω𝜔\omegaitalic_ω-sets associated with context-free languages. Information and Control, 31(3):272–293, 1976.
- Robin Milner. A complete inference system for a class of regular behaviours. Journal of Computer and System Sciences, 28(3):439–466, 1984.
- Damian Niwiński. Fixed-point characterization of context-free ∞\infty∞-languages. Information and control, 61(3):247–276, 1984.
- Ewa Palka. An infinitary sequent system for the equational theory of *-continuous action lattices. Fundamenta Informaticae, 78(2):295–309, 2007.
- Completeness Theorems for Kleene Algebra with Top. In Bartek Klin, Sławomir Lasota, and Anca Muscholl, editors, 33rd International Conference on Concurrency Theory (CONCUR 2022), volume 243 of Leibniz International Proceedings in Informatics (LIPIcs), pages 26:1–26:18, Dagstuhl, Germany, 2022. Schloss Dagstuhl – Leibniz-Zentrum für Informatik.
- Georg Struth. Left omega algebras and regular equations. The Journal of Logic and Algebraic Programming, 81(6):705–717, 2012. 12th International Conference on Relational and Algebraic Methods in Computer Science (RAMiCS 2011).
- Thomas Studer. On the proof theory of the modal mu-calculus. Studia Logica, 89(3):343–363, 2008.
- Alfred Tarski. On the calculus of relations. Journal of Symbolic Logic, 6(3):73–89, 1941.
- Propositional Dynamic Logic. In Edward N. Zalta and Uri Nodelman, editors, The Stanford Encyclopedia of Philosophy. Metaphysics Research Lab, Stanford University, Fall 2023 edition, 2023.
- Klaus W. Wagner. Eine axiomatisierung der theorie der regulären folgenmengen. J. Inf. Process. Cybern., 12(7):337–354, 1976.
- Christian Wurm. Kleene algebras, regular languages and substructural logics. Electronic Proceedings in Theoretical Computer Science, 161:46–59, August 2014.