The complementation problem for nondeterministic word automata has numerous applications in formal verification. In particular, the language-containment problem, to which many verification problems are reduced, involves complementation. For automata on finite words, which correspond to safety properties, complementation involves determinization. The 2 blow-up that is caused by the subset constr...

An extension to finite state transducers is presented, in which atomic symbols are replaced by arbitrary predicates over symbols. The extension is motivated by applications in natural language processing (but may be more widely applicable) as well as by the observation that transducers with predicates generally have fewer states and fewer transitions. Although the extension is fairly trivial fo...

We show how to calculate the maximum number of edits per character needed to convert any string in one regular language to a string in another language. Our algorithm makes use of a local determinization procedure applicable to a subclass of distance automata. We then show how to calculate the same property when the editing needs to be done in streaming fashion, by a finite state transducer, us...

Nested-word automata (NWAs) are a language formalism that helps bridge the gap between finite-state automata and pushdown automata. NWAs can express some context-free properties, such as parenthesis matching, yet retain all the desirable closure characteristics of finite-state automata. This paper describes OpenNWA, a C++ library for working with NWAs. The library provides the expected automata...

In this paper, we first introduce a new lower bound technique for the state complexity of transformations of automata. Namely we suggest considering the class of full automata in lower bound analysis. Then we apply such technique to the complementation of nondeterministic ωautomata and obtain several lower bound results. Particularly, we prove anΩ((0.76n)) lower bound for Büchi complementation,...

In this paper, we develop the basic theory of disimulations, a type of relation between two automata which witnesses equivalence. We show that many standard constructions in the theory of automata such as determinization, minimization, inaccessible state removal, et al., are instances of disimilar automata. Then, using disimulations, we define an “algebraic” proof system for the equational theo...

We present a disambiguation algorithm for weighted finite tree automata (FTA). This algorithm converts ambiguous FTA into equivalent non-ambiguous one where no two accepting paths labeled with the same tree exists. The notion of non-ambiguity is similar to that of determinism in the automata theory, but we show that disambiguation is applicable to the wider class of weighted automata than deter...

In this work we present the use of a specialized composition algorithm that allows the generation of a determinized search network for ASR in a single step. The algorithm is exact in the sense that the result is determinized when the lexicon and the language model are represented as determinized transducers. The composition and determinization are performed simultaneously, which is of great imp...

Visibly pushdown automata (VPA), introduced by Alur and Madhusuan in 2004, is a subclass of pushdown automata whose stack behavior is completely determined by the input symbol according to a fixed partition of the input alphabet. Since its introduce, VPAs have been shown to be useful in various context, e.g., as specification formalism for verification and as automaton model for processing XML ...

Timed automata are known not to be complementable or determinizable. Natural questions are, then, could we check whether a given TA enjoys these properties? These problems are not algorithmically solvable. Minimizing the “resources” of a TA (number of clocks or size of constants) are also unsolvable problems. In this paper we provide simple undecidability proofs using a “constructive” version o...