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Autour des automates : génération aléatoire et contribution à quelques extensions

Abstract : The subject of this thesis is decided into three parts: two of them are about extensions of the classical model in automata theory, whereas the third one is about a more concrete aspect which consists in randomly generate automata with specific properties. We first give an extension of the universal automaton on finite words to infinite words. To achieve this, we define a normal form in order to take account of the specific acceptance mode of Büchi automata which recognize omega-langages. Then we define two kinds of omega-factorizations, a "regular" one and the "pure" kind, which are both extensions of the classical concept of factorization of a language. This let us define the universal automaton of an omega-language. We prove that it has all the required properties: it is the smallest Buchi automaton, in normal form, that recognizes the omega-language and which has the universal property. We also give an effective way to compute the "regular" omega-factorizations of a language using a prophetic automaton recognizing the language. In the second part, we deal with two-way automata weighted over a semi ring. First, we give a slightly different version of the computation of a weighted one-way automaton from a weighted two-way automaton and we prove that it preserves the non-ambiguity but not the determinism. We prove that non-ambiguous weighted two-way automata are equivalent to deterministic weighted one-way automata. In a later part, we focus on tropical semi rings (or min-+). We prove that two-way automata on N-min-+ are equivalent to one-way automata on N-min-+. We also prove that the behavior of two-way automata on Z-min-+ are not always defined and that this property is decidable whereas it is undecidable whether or not there exists a word on which the behavior is defined. In the last section, we propose an algorithm in order to randomly generate acyclic, accessible and determinist automata and minimal acyclic automata with an almost uniform distribution using Morkov chains. We prove the reliability of both algorithms and we explain how to adapt them in order to fit with constraints on the set of final states
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Vincent Carnino. Autour des automates : génération aléatoire et contribution à quelques extensions. Autre [cs.OH]. Université Paris-Est, 2014. Français. ⟨NNT : 2014PEST1079⟩. ⟨tel-01124015⟩



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