LOGIC and P-RECOGNIZABLE SETS of INTEGERS 1 Introduction
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On a Subclass of Context-Free Groups Informatique Théorique Et Applications, Tome 25, No 3 (1991), P
INFORMATIQUE THÉORIQUE ET APPLICATIONS THOMAS HERBST On a subclass of context-free groups Informatique théorique et applications, tome 25, no 3 (1991), p. 255-272 <http://www.numdam.org/item?id=ITA_1991__25_3_255_0> © AFCET, 1991, tous droits réservés. L’accès aux archives de la revue « Informatique théorique et applications » im- plique l’accord avec les conditions générales d’utilisation (http://www.numdam. org/conditions). Toute utilisation commerciale ou impression systématique est constitutive d’une infraction pénale. Toute copie ou impression de ce fichier doit contenir la présente mention de copyright. Article numérisé dans le cadre du programme Numérisation de documents anciens mathématiques http://www.numdam.org/ Informatique théorique et Applications/Theoretical Informaties and Applications (vol. 25, n° 3, 1991, p. 255 à 272) ON A SUBCLASS OF CONTEXT-FREE GROUPS (*) by Thomas HERBST (*) Communicated by J. BERSTEL Abstract. - We investigate those groups which are finite or finite extensions of Z. We give several char acier izations of this cîass in terms of formai languages and automata theory, and show that, from a formai language point of view, this is the most important class of groups between context-free and finite groups. Résumé. - Nous examinons les groupes finis, ou qui sont extensions finies du groupe Z. Nous donnons plusieurs caractérisations de cette classe, soit en termes de langages formels, soit en termes de la théorie des automates, et nous montrons que, du point de vue des langages formels, ces groupes forment la classe la plus importante entre les groupes context-free et les groupes finis. 1. INTRODUCTION Following Muller and Schupp [19] we define the word problem of a group G in a given présentation to be the set of words which are equivalent to the unit of G. -
Formal Languages Defined by Uniform Substitutions
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector Theoretical Computer Science 132 (1994) 243-258 243 Elsevier Formal languages defined by uniform substitutions Jean-Camille Birget” Department ofComputer Science and Engineering, University of’ Nebraska, Lincoln, NE 68588-0115, USA Joseph B. Stephen Department qfMathematica1 Sciences, Northern Illinois University, DeKalb, IL 601152888, USA Communicated by A. Salomaa Received January 1993 Revised June 1993 Abstract J.-C. Birget and J.B. Stephen, Formal languages defined by uniform substitutions, Theoretical Computer Science 132 (1994) 243-258. When a uniform substitution is applied to a word, the same letter at different positions in the word is transformed everywhere in the same way. Thus, a uniform substitution SH is determined by a set H of homomorphisms. We define recognizable and rational sets of homomorphisms and we prove closure and non-closure properties of the class of languages of the form S,(L), where L is regular and H is recognizable. We also show that in this case (and in more general situations as well) the membership problem for S,(L) is solvable in deterministic polynomial time. 1. Introduction and definitions A classical, non-uniform, substitution is a function S : V*+P(Z*) satisfying S(u . v) = S(u). S(v) for all U, VE V*, and S(E)=&. Notation: V and C are finite alphabets; V* (respectively C*) is the set of all words over I/ (respectively C); P(C*) is the power set of C*; the dot - denotes concatenation; E is the empty word. -
Rational, Recognizable, and Aperiodic Sets in the Partially Lossy Queue Monoid
Köcher, Chris: Rational, recognizable, and aperiodic sets in the partially lossy queue monoid Original published in: 35th Symposium on Theoretical Aspects of Computer Science / STACS 35, 2018 Caen, France. - Saarbrücken/Wadern, Germany : Schloss Dagstuhl - Leibniz-Zentrum für Informatik GmbH, Dagstuhl Publishing, February, 2018. - (2018), art. 45, 14 pp. ISBN 978-3-95977-062-0 (Leibniz International Proceedings in Informatics (LIPIcs) ; 96) Original published: February 2018 ISSN: 1868-8969 DOI: 10.4230/LIPIcs.STACS.2018.45 [Visited: 2020-03-02] This work is licensed under a Creative Commons Attribution 3.0 Unported license. To view a copy of this license, visit http://creativecommons.org/licenses/BY/3.0/ TU Ilmenau | Universitätsbibliothek | ilmedia, 2020 http://www.tu-ilmenau.de/ilmedia Rational, Recognizable, and Aperiodic Sets in the Partially Lossy Queue Monoid Chris Köcher Technische Universität Ilmenau, Automata and Logics Group [email protected] Abstract Partially lossy queue monoids (or plq monoids) model the behavior of queues that can forget arbitrary parts of their content. While many decision problems on recognizable subsets in the plq monoid are decidable, most of them are undecidable if the sets are rational. In particular, in this monoid the classes of rational and recognizable subsets do not coincide. By restricting multiplication and iteration in the construction of rational sets and by allowing complementation we obtain precisely the class of recognizable sets. From these special rational expressions we can -
Synchronized Rational Relations of Finite and Infinite Words*
Theoretical Computer Science 108 (1993) 45-82 45 Elsevier Synchronized rational relations of finite and infinite words* Christiane Frougny UniversitC Paris 8 and Laboratoire It@rmatique Thkorique et Programnation. Institut Blake Pascal, 4 place Jussieu. 75252 Paris Cedes 05. France Jacques Sakarovitch CNRS, Institut Blake Pascal, 4 place Jussieu. 75252 Paris Cedes OS, France Abstract Frougny, Ch. and J. Sakarovitch, Synchronized rational relations of finite and infinite words, Theoretical Computer Science 108 (1993) 45-82. The purpose of this paper is a comprehensive study of a family of rational relations, both of finite and infinite words, namely those that are computable by automata where the reading heads move simultaneously on the n input tapes, and that we thus propose to call synchronized rational relations. Introduction Rational relations on words are those relations that are computable by finite automata with two or more l-way input tapes. These relations have been considered by Rabin and Scott [20], who stated in their survey paper a number of results and problems, the last of which - the equivalence of deterministic n-tape automata - has been solved only recently [14]. The first systematic study is due to Elgot and Mezei [7], who established in their seminal paper of 1965 a number of properties of these relations, among which the closure by composition. Both these papers deal with finite words, whereas Biichi considered, for his investigation of second-order logic, com- putations of finite automata on n-tuples of infinite words [4]. The purpose of this paper is a comprehensive study of a family of rational relations, both of finite and infinite words, namely those that are computable by automata with Correspondence to: Ch. -
On Finitely Generated Submonoids of Virtually Free Groups
On finitely generated submonoids of virtually free groups Pedro V. Silva1, Alexander Zakharov2 Centre of Mathematics, University of Porto, R. Campo Alegre 687, 4169-007 Porto, Portugal Abstract We prove that it is decidable whether or not a finitely generated submonoid of a virtually free group is graded, introduce a new geometric characterization as quasi- geodesic monoids, and show that their word problem is rational (as a relation). We also solve the isomorphism problem for this class of monoids, generalizing earlier results for submonoids of free monoids. We also prove that the classes of graded monoids, regular monoids and Kleene monoids coincide for submonoids of free groups. MSC: 20E05; 20M05; 20F10; 68Q45; 68Q70 Keywords: Free group; virtually free group; submonoids; graded monoid; rational monoid; Kleene monoids; decidability 1 Introduction A lot is known about subgroups of free groups. And the seminal work of Stallings [21] provided the tools to expand that knowledge in multiple directions, particularly when au- tomata got into the picture (see [2], [9]). This glorious picture fades away when we change from subgroups to submonoids, even in the finitely generated case. Indeed, we cannot use anymore inverse automata and that is a major setback. The membership problem is still decidable, as a consequence of Benois’ Theorem (see [17, Theorem 6.1, p.314]), but e.g. the isomorphism problem remains open. On the other hand, submonoids of virtually free groups (i.e. groups admitting a free subgroup of finite index) have been studied in [5]. In this paper, we explore a subclass of finitely generated submonoids of virtually free groups which is somehow in the antipodals of subgroups. -
Inverse Monoids, Trees, and Context-Free Languages
transactions of the american mathematical society Volume 335, Number 1, January 1993 INVERSE MONOIDS, TREES, AND CONTEXT-FREE LANGUAGES STUART W. MARGOLIS AND JOHN C. MEAKIN Abstract. This paper is concerned with a study of inverse monoids presented by a set X subject to relations of the form e¡ = f¡, i € I, where e¡ and f¡ are Dyck words, i.e. idempotents of the free inverse monoid on X . Some general results of Stephen are used to reduce the word problem for such a presentation to the membership problem for a certain subtree of the Cayley graph of the free group on X . In the finitely presented case the word problem is solved by using Rabin's theorem on the second order monadic logic of the infinite binary tree. Some connections with the theory of rational subsets of the free group and the theory of context-free languages are explored. 1. Introduction We refer the reader to Lallement [5] for basic information about semigroups and connections with automata theory and formal language theory. We shall be concerned in this paper primarily with inverse semigroups and inverse monoids. For the convenience of the reader we briefly summarize the basic notions and results about inverse monoids that we will need in the present paper; many more details and results about inverse monoids may be found in the book of Petrich [9]- An inverse semigroup is a semigroup S with the property that, for each a eS there is a unique element a~x £ S such that a = aa~xa and a~x = a~xaa~x. -
On the Structure and Complexity of Rational Sets of Regular Languages
On the Structure and Complexity of Rational Sets of Regular Languages Andreas Holzer1, Christian Schallhart2, Michael Tautschnig3, and Helmut Veith1 1 Vienna University of Technology, Austria 2 University of Oxford, UK 3 Queen Mary, University of London, UK Abstract In the recently designed and implemented test specification language FQL, relevant test goals are specified as regular expressions over program locations. To transition from single test goals to test suites, FQL describes suites as regular expressions over finite alphabets where each symbol corresponds to a regular expression over program locations. Hence, each word in a test suite expression yields a test goal specification. Such test suite specifications are in fact rational sets of regular languages (RSRLs). We show closure properties of general and finite RSRLs under common set theoretic operations. We also prove complexity results for checking equivalence and inclusion of star-free RSRLs and for checking whether a regular language is a member of a general or star-free RSRL. As the star-free (and thus finite) case underlies FQL specifications, the closure and complexity results provide a systematic foundation for FQL test specifications. 1998 ACM Subject Classification F.4.3 Formal Languages Keywords and phrases Rational Sets, Regular Languages, Test Specification in FQL, Closure Properties, Decision Problems Digital Object Identifier 10.4230/LIPIcs.FSTTCS.2013.377 1 Introduction Despite the success of model checking and theorem proving, software testing has a dominant role in industrial practice. In fact, state-of-the-art development guidelines such as the avionic standard DO-178B [27] are heavily dependent on test coverage criteria. -
On the Structure and Complexity of Rational Sets of Regular Languages
On the Structure and Complexity of Rational Sets of Regular Languages Andreas Holzer1, Christian Schallhart2, Michael Tautschnig3, and Helmut Veith1 1 Vienna University of Technology, Austria 2 University of Oxford, UK 3 Queen Mary, University of London, UK Abstract In the recently designed and implemented test specification language FQL, relevant test goals are specified as regular expressions over program locations. To transition from single test goals to test suites, FQL describes these as regular expressions over alphabets where each symbol corresponds to a regular expression over program locations. Hence, each word in a test suite expression is a test goal specification. Such test suite specifications are in fact rational sets of regular languages (RSRLs). We show closure properties of RSRLs under common set theoretic operations for general and finite RSRLs. We also prove complexity results for checking equivalence and inclusion of star-free RSRLs and for checking whether a regular language is member of a general or star- free RSRL. As the star-free (and thus finite) case underlies FQL specifications, we provide a systematic foundation for FQL test specifications. 1998 ACM Subject Classification F.4.3 Formal Languages Keywords and phrases Rational Sets, Regular Languages, Test Specification in FQL, Closure Properties, Decision Problems Digital Object Identifier 10.4230/LIPIcs.xxx.yyy.p 1 Introduction Despite the success of model checking and theorem proving, software testing has a dominant role in industrial practice. In fact, state-of-the-art development guidelines such as the avionic standard DO-178B [28] are heavily dependent on test coverage criteria. It is therefore quite surprising that the formal specification of coverage criteria has been a blind spot in the formal methods and software engineering communities for a long time. -
Theoretical Computer Science the Parikh Counting Functions Of
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector Theoretical Computer Science 410 (2009) 5158–5181 Contents lists available at ScienceDirect Theoretical Computer Science journal homepage: www.elsevier.com/locate/tcs The Parikh counting functions of sparse context-free languages are quasi-polynomialsI Flavio D'Alessandro a,∗,1, Benedetto Intrigila b,1, Stefano Varricchio b a Dipartimento di Matematica, Università di Roma ``La Sapienza'', Piazzale Aldo Moro 2, 00185 Roma, Italy b Dipartimento di Matematica, Università di Roma ``Tor Vergata'', via della Ricerca Scientifica, 00133 Roma, Italy article info a b s t r a c t t Article history: Let L be a sparse context-free language over an alphabet of t letters and let fL V N ! N be Received 11 July 2008 its Parikh counting function. We prove the following two results: Received in revised form 7 July 2009 t Accepted 2 September 2009 1. There exists a partition of N into a finite family of polyhedra such that the function fL Communicated by D. Perrin is a quasi-polynomial on each polyhedron of the partition. t 2. There exists a partition of N into a finite family of rational subsets such that the function Keywords: fL is a polynomial on each set of the partition. Sparse language Context-free language ' 2009 Elsevier B.V. All rights reserved. Semi-linear set Parikh counting function 1. Introduction In this paper, we study some combinatorial and decision problems concerning the Parikh counting functions of formal languages. Given an alphabet A D fa1;:::; at g and a word w over A, the Parikh vector of w is the vector .n1;:::; nt /, such that, for every i with 1 ≤ i ≤ t, ni is the number of occurrences of the letter ai in w. -
Group Presentations, Formal Languages and Characterizations of One-Counter Groups
CORE Metadata, citation and similar papers at core.ac.uk Provided by Elsevier - Publisher Connector Theoretical Computer Science 112 (1993) 1877213 Elsevier Fundamental Study Group presentations, formal languages and characterizations of one-counter groups Thomas Herbst Communicated by M. Nivat Received January 1992 Herhst, T. and R.M. Thomas. Group presentations, formal languages and characterizations of one-counter groups, Theoretical Computer Science II2 (1993) 1877213. In this paper, we give a survey of various connections between the theories of group presentations and formal languages, concentrating on groups in which the word problem is a regular, one-counter or context-free language. We also prove some new results on one-counter groups. Contents I. Introduction ....... 188 2. Classification of groups by formal languages ....... 194 3. Rational and recognizable sets ....... 196 4. Ends and context-free groups ....... 198 5. One-counter groups ....... 201 6. Rational and recognizable sets in groups ....... 204 7. Star-height ....... 206 References ..................................................................... 212 Cor~?spondencr to: T. Herbst, Department VS;EDBl. Standard Elektrik Lorenz AG, PO Box 40 07 49, D-7000 Stuttgart 40, Germany. 0304-3975.!93,‘$06.00 I(_ 1993-Elsevier Science Publishers B.V. All rights reserved 188 T. Hrrhsr,R.M. Thnua 1. Introduction The purpose of this paper is to try and survey some connections between formal language theory and group theory. These connections have been richly exploited (see [l-4,7, 12, 15, 16, 1%20,29,30.33-351 for example), and we hope to illustrate some of them, as well as proving some new results about one-counter groups. -
Rational Subsets of Groups, When Good Closure and Decidability Properties of These Subsets Are Satisfied
Rational subsets of groups L. Bartholdi1 P. V. Silva2,∗ 1Mathematisches Institut Georg-August Universit¨at zu G¨ottingen Bunsenstraße 3–5 D-37073 G¨ottingen, Germany email: [email protected] 2Centro de Matem´atica, Faculdade de Ciˆencias Universidade do Porto R. Campo Alegre 687 4169-007 Porto, Portugal email: [email protected] 2010 Mathematics Subject Classification: 20F10, 20E05, 68Q45, 68Q70 Key words: Free groups, inverse automata, Stallings automata, rational subsets. Contents 1 Finitely generated groups 2 1.1 Freegroups ................................. 3 2 Inverse automata and Stallings’ construction 4 2.1 Inverseautomata .............................. 4 2.2 Stallings’construction. .. 5 2.3 Basicapplications.............................. 7 2.4 Conjugacy.................................. 10 2.5 Furtheralgebraicproperties . ... 12 2.6 Topologicalproperties. 14 2.7 Dynamicalproperties ............................ 16 3 Rational and recognizable subsets 17 3.1 Rationalandrecognizablesubgroups . .... 18 3.2 Benois’Theorem .............................. 19 3.3 Rationalversusrecognizable . .. 21 arXiv:1012.1532v1 [cs.FL] 7 Dec 2010 3.4 Beyondfreegroups ............................. 22 3.5 Rationalsolutionsetsandrationalconstraints . ......... 24 References 25 ∗The second author acknowledges support by Project ASA (PTDC/MAT/65481/2006) and C.M.U.P., fi- nanced by F.C.T. (Portugal) through the programmes POCTI and POSI, with national and E.U. structural funds. 2 L. Bartholdi, P. V. Silva Over the years, finite automata have been used effectively in the theory of infinite groups to represent rational subsets. This includes the important particular case of finitely generated subgroups (and the beautiful theory of Stallings automata for the free group case), but goes far beyond that: certain inductive procedures need a more general set- ting than mere subgroups, and rational subsets constitute the natural generalization. -
Algebraic Recognizability of Languages Pascal Weil
Algebraic recognizability of languages Pascal Weil To cite this version: Pascal Weil. Algebraic recognizability of languages. Mathematical Foundations of Computer Science 2004, 2004, Prague, Czech Republic. pp.149-175. hal-00096619 HAL Id: hal-00096619 https://hal.archives-ouvertes.fr/hal-00096619 Submitted on 19 Sep 2006 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Algebraic Recognizability of Languages⋆ Pascal Weil LaBRI, CNRS and Universit´eBordeaux-1, [email protected] Abstract. Recognizable languages of finite words are part of every com- puter science cursus, and they are routinely described as a cornerstone for applications and for theory. We would like to briefly explore why that is, and how this word-related notion extends to more complex models, such as those developed for modeling distributed or timed behaviors. Ò ÖÕ Ò Ð º º In the beginning was the Word. Recognizable languages of finite words are part of every computer science cursus, and they are routinely described as a cornerstone for applications and for theory. We would like to briefly explore why that is, and how this word- related notion extends to more complex models, such as those developed for modeling distributed or timed behaviors.