251 research outputs found
State-deterministic Finite Automata with Translucent Letters and Finite Automata with Nondeterministically Translucent Letters
Deterministic and nondeterministic finite automata with translucent letters
were introduced by Nagy and Otto more than a decade ago as Cooperative
Distributed systems of a kind of stateless restarting automata with window size
one. These finite state machines have a surprisingly large expressive power:
all commutative semi-linear languages and all rational trace languages can be
accepted by them including various not context-free languages. While the
nondeterministic variant defines a language class with nice closure properties,
the deterministic variant is weaker, however it contains all regular languages,
some non-regular context-free languages, as the Dyck language, and also some
languages that are not even context-free. In all those models for each state,
the letters of the alphabet could be in one of the following categories: the
automaton cannot see the letter (it is translucent), there is a transition
defined on the letter (maybe more than one transitions in nondeterministic
case) or none of the above categories (the automaton gets stuck by seeing this
letter at the given state and this computation is not accepting).
State-deterministic automata are recent models, where the next state of the
computation determined by the structure of the automata and it is independent
of the processed letters. In this paper our aim is twofold, on the one hand, we
investigate state-deterministic finite automata with translucent letters. These
automata are specially restricted deterministic finite automata with
translucent letters.
In the other novel model we present, it is allowed that for a state the set
of translucent letters and the set of letters for which transition is defined
are not disjoint. One can interpret this fact that the automaton has a
nondeterministic choice for each occurrence of such letters to see them (and
then erase and make the transition) or not to see that occurrence at that time.
Based on these semi-translucent letters, the expressive power of the automata
increases, i.e., in this way a proper generalization of the previous models is
obtained.Comment: In Proceedings AFL 2023, arXiv:2309.0112
Commutative Languages and their Composition by Consensual Methods
Commutative languages with the semilinear property (SLIP) can be naturally
recognized by real-time NLOG-SPACE multi-counter machines. We show that unions
and concatenations of such languages can be similarly recognized, relying on --
and further developing, our recent results on the family of consensually
regular (CREG) languages. A CREG language is defined by a regular language on
the alphabet that includes the terminal alphabet and its marked copy. New
conditions, for ensuring that the union or concatenation of CREG languages is
closed, are presented and applied to the commutative SLIP languages. The paper
contributes to the knowledge of the CREG family, and introduces novel
techniques for language composition, based on arithmetic congruences that act
as language signatures. Open problems are listed.Comment: In Proceedings AFL 2014, arXiv:1405.527
Restarting Automata with Auxiliary Symbols and Small Lookahead
We present a study on lookahead hierarchies for restarting automata with
auxiliary symbols and small lookahead. In particular, we show that there are
just two different classes of languages recognised RRWW automata, through the
restriction of lookahead size. We also show that the respective (left-)
monotone restarting automaton models characterise the context-free languages
and that the respective right-left-monotone restarting automata characterise
the linear languages both with just lookahead length 2.Comment: Full version of the paper accepted to LATA 201
Prostredie pre reštartovacie automaty
Reštartovacie automaty sĂş lingvisticky motivovanĂ© modely automatov, ktorĂ© mĂ´Ĺľu byĹĄ pouĹľitĂ© naprĂklad na kontrolu správnosti viet. HlavnĂ˝m cieÄľom tejto práce je vytvoriĹĄ špecializovanĂ˝ program, ktorĂ˝ umoĹľnĂ jednoduchĂ˝ interaktĂvny návrh a testovanie tĂ˝chto automatov a poskytne špecializovanĂ© nástroje urÄŤenĂ© na uÄŤenie koneÄŤnĂ˝ch automatov a definovanie jazykov. Práca prezentuje teoretickĂ© základy a uvádza formálnu definĂciu reštartovacieho automatu. ÄŽalej sĂş v práci diskutovanĂ© moĹľnosti implementácie takĂ©hoto systĂ©mu a je popĂsaná skutoÄŤná realizácia systĂ©mu. K práci je priloĹľená uĹľĂvateÄľská prĂruÄŤka.Restarting automata are linguistically motivated models of automata that can be used e.g. in checking correctness of a sentence. The main subject of this work is to design a specialized program which allows an easy design and testing of these automata and provides specialized tools for learning finite automata and defining languages. The thesis presents theoretical background and gives formal definition of restarting automaton. Then the possibilities of implementation of such system are discussed and the actual implementation is described. The user guide is included in the thesis.Katedra softwaru a vĂ˝uky informatikyDepartment of Software and Computer Science EducationFaculty of Mathematics and PhysicsMatematicko-fyzikálnĂ fakult
Clearing Restarting Automata
RestartovacĂ automaty byly navrĹľeny jako model pro redukÄŤnĂ analĂ˝zu, která pĹ™edstavuje lingvisticky motivovanou metodu pro kontrolu korektnosti vÄ›ty. CĂlem práce je studovat omezenÄ›jšà modely restartovacĂch automatĹŻ, kterĂ© smĂ vymazat podĹ™etÄ›zec nebo jej nahradit speciálnĂm pomocnĂ˝m symbolem, jenom na základÄ› omezenĂ©ho lokálnĂho kontextu tohoto podĹ™etÄ›zce. Tyto restartovacĂ automaty se nazĂ˝vajĂ clearing restarting automata. V práci jsou taktĂ©Ĺľ zkoumány uzávÄ›rovĂ© vlastnosti tÄ›chto automatĹŻ, jejich vztah k Chomskeho hierarchii a moĹľnosti uÄŤenĂ tÄ›chto automatĹŻ na základÄ› pozitivnĂch a negativnĂch pĹ™ĂkladĹŻ.Restarting automata were introduced as a model for analysis by reduction which is a linguistically motivated method for checking correctness of a sentence. The goal of the thesis is to study more restricted models of restarting automata which based on a limited context can either delete a substring of the current content of its tape or replace a substring by a special symbol, which cannot be overwritten anymore, but it can be deleted later. Such restarting automata are called clearing restarting automata. The thesis investigates the properties of clearing restarting automata, their relation to Chomsky hierarchy and possibilities for machine learning of such automata from positive and negative samples.Department of Software and Computer Science EducationKatedra softwaru a vĂ˝uky informatikyFaculty of Mathematics and PhysicsMatematicko-fyzikálnĂ fakult
Supistavan äärellistilaisen dependenssijäsentimen suunnittelun tarkennusta
Proceeding volume: 2012This work complements a parallel paper of a new finite-state dependency parser architecture (Yli-Jyrä, 2012) by a proposal for a linguistically elaborated morphology-syntax interface and its finite-state implementation. The proposed interface extends Gaifman’s (1965) classical dependency rule formalism by separating lexical word forms and morphological categories from syntactic categories. The separation lets the linguist take advantage of the morphological features in order to reduce the number of dependency rules and to make them lexically selective. In addition, the relative functional specificity of parse trees gives rise to a measure of parse quality. By filtering worse parses out from the parse forest using finite-state techniques, the best parses are saved. Finally, we present a synthesis of strict grammar parsing and robust text parsing by connecting fragmental parses into trees with additional linear successor links.Peer reviewe
Automatic Semigroups vs Automaton Semigroups
We develop an effective and natural approach to interpret any semigroup admitting a special language of greedy normal forms as an automaton semigroup, namely the semigroup generated by a Mealy automaton encoding the behaviour of such a language of greedy normal forms under one-sided multiplication. The framework embraces many of the well-known classes of (automatic) semigroups: free semigroups, free commutative semigroups, trace or divisibility monoids, braid or Artin - Tits or Krammer or Garside monoids, Baumslag - Solitar semigroups, etc. Like plactic monoids or Chinese monoids, some neither left- nor right-cancellative automatic semigroups are also investigated, as well as some residually finite variations of the bicyclic monoid. It provides what appears to be the first known connection from a class of automatic semigroups to a class of automaton semigroups. It is worthwhile noting that, "being an automatic semigroup" and "being an automaton semigroup" become dual properties in a very automata-theoretical sense. Quadratic rewriting systems and associated tilings appear as the cornerstone of our construction
IST Austria Technical Report
We consider partially observable Markov decision processes (POMDPs), that are a standard framework for robotics applications to model uncertainties present in the real world, with temporal logic specifications. All temporal logic specifications in linear-time temporal logic (LTL) can be expressed as parity objectives. We study the qualitative analysis problem for POMDPs with parity objectives that asks whether there is a controller (policy) to ensure that the objective holds with probability 1 (almost-surely). While the qualitative analysis of POMDPs with parity objectives is undecidable, recent results show that when restricted to finite-memory policies the problem is EXPTIME-complete. While the problem is intractable in theory, we present a practical approach to solve the qualitative analysis problem. We designed several heuristics to deal with the exponential complexity, and have used our implementation on a number of well-known POMDP examples for robotics applications. Our results provide the first practical approach to solve the qualitative analysis of robot motion planning with LTL properties in the presence of uncertainty
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