ω-automaton

About: ω-automaton is a research topic. Over the lifetime, 2299 publications have been published within this topic receiving 68468 citations. The topic is also known as: stream automaton & ω-automata.

Determinizing Asynchronous Automata on Infinite Inputs

Abstract: Asynchronous automata are a natural distributed machine model for recognizing trace languages - languages defined over an alphabet equipped with an independence relation. To handle infinite traces, Gastin and Petit introduced Buchi asynchronous automata, which accept precisely the class of omega-regular trace languages. Like their sequential counterparts, these automata need to be non-deterministic in order to capture all omega-regular languages. Thus complementation of these automata is non-trivial. Complementation is an important operation because it is fundamental for treating the logical connective "not" in decision procedures for monadic second-order logics. Subsequently, Diekert and Muscholl solved the complementation problem by showing that with a Muller acceptance condition, deterministic automata suffice for recognizing omega-regular trace languages. However, a direct determinization procedure, extending the classical subset construction, has proved elusive. In this paper, we present a direct determinization procedure for Buchi asynchronous automata, which generalizes Safra's construction for sequential Buchi automata. As in the sequential case, the blow-up in the state space is essentially that of the underlying subset construction.

Computing the Rabin Index of a Regular Language of Infinite Words

Abstract: The Rabin index of a regular language of infinite words is the minimum number of accepting pairs used in any deterministic Rabin automaton recognizing this language. We show that the Rabin index of a language given by a Muller automaton withnstates andmaccepting sets is computable in timeO(m2nc) wherecis the cardinality of the alphabet.

Fresh-Variable Automata: Application to Service Composition

Abstract: We introduce fresh-variable automata, a natural extension of finite-state automata over infinite alphabet. In this model the transitions are labeled with constants or variables that can be refreshed in some specified states. We prove several closure properties for this class of automata and study their decision problems. We show the applicability of our model in modeling Web services handling data from an infinite domain. We introduce a notion of simulation that enables us to reduce the Web service composition problem to the construction of a simulation of a target service by the asynchronous product of existing services, and prove that this construction is computable.

Automata theory and higher-order model-checking

Abstract: In verification, an automata theoretic approach is by now a standard. In order to extend this approach to higher-order programs we need a good understanding of higher-order control flow, and for this semantics has the right tools. We present some results and methods of this subject between automata theory and semantics.

Experiments on Synchronizing Automata

Abstract: This work is motivated by the ˇ Cerny Conjecture - an old unsolved problem in the automata theory. We describe the results of the experiments on synchronizing automata, which have led us to two interesting results. The first one is that the size of an automaton al- phabet may play an important role in the issue of synchronization: we have found a 5-state automaton over a 3-letter alphabet which attains the upper bound from the ˇ Cerny Conjecture, while there is no such automaton (except ˇ Cerny automaton C5) over a binary alphabet. The second result emerging from the experiments is a theorem describing the dependencies between the automaton structure S expressed in terms of the so-called merging system and the maximal length of all minimal synchronizing words for automata of type S.