Search results for "formal languages"

Languages with mismatches and an application to approximate indexing

2005

In this paper we describe a factorial language, denoted by L(S, k,r), that contains all words that occur in a string 5 up to k mismatches every r symbols. Then we give some combinatorial properties of a parameter, called repetition index and denoted by R(S,k,r), defined as the smallest integer h ? 1 such that all strings of this length occur at most in a unique position of the text S up to k mismatches every r symbols. We prove that R(S, k, r) is a non-increasing function of r and a non-decreasing function of k and that the equation r = R(S, k, r) admits a unique solution. The repetition index plays an important role in the construction of an indexing data structure based on a trie that rep…

Finite automata on timed ω-trees

2003

AbstractIn the last decade Alur and Dill introduced a model of automata on timed ω-sequences which extends the traditional models of finite automata. In this paper, we present a theory of timed ω-trees which extends both the theory of timed ω-sequences and the theory of ω-trees. The main motivation is to introduce a new way of specifying real-time systems and provide tools for studying decidability problems in related fields. We focus on the decision problems and their applications in system verification and synthesis.

RECOGNIZABLE PICTURE LANGUAGES

1992

The purpose of this paper is to propose a new notion of recognizability for picture (two-dimensional) languages extending the characterization of one-dimensional recognizable languages in terms of local languages and alphabetic mappings. We first introduce the family of local picture languages (denoted by LOC) and, in particular, prove the undecidability of the emptiness problem. Then we define the new family of recognizable picture languages (denoted by REC). We study some combinatorial and language theoretic properties of REC such as ambiguity, closure properties or undecidability results. Finally we compare the family REC with the classical families of languages recognized by four-way a…

Cancellation, pumping and permutation in formal languages

1984

The Intersection of $3$-Maximal Submonids

2020

Very little is known about the structure of the intersection of two $k$-generated monoids of words, even for $k=3$. Here we investigate the case of $k$-maximal monoids, that is, monoids whose basis of cardinality $k$ cannot be non-trivially decomposed into at most $k$ words. We characterize the intersection in the case of two $3$-maximal monoids.

Exact results for accepting probabilities of quantum automata

2001

One of the properties of Kondacs-Watrous model of quantum finite automata (QFA) is that the probability of the correct answer for a QFA cannot be amplified arbitrarily. In this paper, we determine the maximum probabilities achieved by QFAs for several languages. In particular, we show that any language that is not recognized by an RFA (reversible finite automaton) can be recognized by a QFA with probability at most 0.7726...

Word assembly through minimal forbidden words

2006

AbstractWe give a linear-time algorithm to reconstruct a finite word w over a finite alphabet A of constant size starting from a finite set of factors of w verifying a suitable hypothesis. We use combinatorics techniques based on the minimal forbidden words, which have been introduced in previous papers. This improves a previous algorithm which worked under the assumption of stronger hypothesis.

Mathematical logic and quantum finite state automata

2009

AbstractThis paper is a review of the connection between formulas of logic and quantum finite-state automata in respect to the language recognition and acceptance probability of quantum finite-state automata. As is well known, logic has had a great impact on classical computation, it is promising to study the relation between quantum finite-state automata and mathematical logic. After a brief introduction to the connection between classical computation and logic, the required background of the logic and quantum finite-state automata is provided and the results of the connection between quantum finite-state automata and logic are presented.

From Nerode's congruence to Suffix Automata with mismatches

2009

AbstractIn this paper we focus on the minimal deterministic finite automaton Sk that recognizes the set of suffixes of a word w up to k errors. As first result we give a characterization of the Nerode’s right-invariant congruence that is associated with Sk. This result generalizes the classical characterization described in [A. Blumer, J. Blumer, D. Haussler, A. Ehrenfeucht, M. Chen, J. Seiferas, The smallest automaton recognizing the subwords of a text, Theoretical Computer Science, 40, 1985, 31–55]. As second result we present an algorithm that makes use of Sk to accept in an efficient way the language of all suffixes of w up to k errors in every window of size r of a text, where r is the…

The Cone Structure Theorem

2020

Made available in DSpace on 2022-05-01T11:54:27Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-07-01 We consider the topological classification of finitely determined map germs f: (Rn, 0) → (Rp, 0) with f-1(0) = {0}. Associated with f we have a link diagram, which is well defined up to topological equivalence. We prove that f is topologically A-equivalent to the generalized cone of its link diagram. Centro de Ciências e Tecnologia Universidade Federal Do Cariri, 63048-080, Juazeiro do Norte Universidade Estadual Paulista (Unesp) Instituto de Biociências Letras e Ciências Exatas Campus de São José Do Rio Preto, 15054-000, São José do Rio Preto Departament de Matemàtiques Universitat …