Showing papers on "Pushdown automaton published in 1992"
TL;DR: An investigation of interactive proof systems (IPSs) where the verifier is a 2-way probabilistic finite state automaton (2pfa) is initiated, and it is shown that IPSs with verifiers in the latter class are as powerful as IPSs where verifiers are polynomial-time Probabilistic Turing machines.
Abstract: An investigation of interactive proof systems (IPSs) where the verifier is a 2-way probabilistic finite state automaton (2pfa) is initiated. In this model, it is shown:(1) IPSs in which the verifier uses private randomization are strictly more powerful than IPSs in which the random choices of the verifier are made public to the prover.(2) IPSs in which the verifier uses public randomization are strictly more powerful than 2pfa's alone, that is, without a prover.(3) Every language which can be accepted by some deterministic Turing machine in exponential time can be accepted by some IPS.Additional results concern two other classes of verifiers: 2pfa's that halt in polynomial expected time, and 2-way probabilistic pushdown automata that halt in polynomial time. In particular, IPSs with verifiers in the latter class are as powerful as IPSs where verifiers are polynomial-time probabilistic Turing machines. In a companion paper [7], zero knowledge IPSs with 2pfa verifiers are investigated.
119 citations
TL;DR: A mathematical definition of left-associative grammar is presented, and its formal properties are described, in contrast to more traditional systems such as phrase structure grammar and categorial grammar, which are linguistically motivated in terms of possible substitutions.
48 citations
Proceedings Article•
30 Nov 1992TL;DR: Some ways in which a priori knowledge about the task and data could be used for efficient learning arediscussed, noting that such knowledge is often an experimental prerequisite for learning nontrivial languages.
Abstract: Although considerable interest has been shown in language inference and automata induction using recurrent neural networks, success of these models has mostly been limited to regular languages. We have previously demonstrated that Neural Network Pushdown Automaton (NNPDA) model is capable of learning deterministic context-free languages (e.g., anbn and parenthesis languages) from examples. However, the learning task is computationally intensive. In this paper we discus some ways in which a priori knowledge about the task and data could be used for efficient learning. We also observe that such knowledge is often an experimental prerequisite for learning nontrivial languages (eg. anbncbmam).
47 citations
TL;DR: The class of exponential-time languages or, equivalently, the class of languages accepted by alternating pushdown automata (APDAs), is exactly theclass of languages generated by linear-erasing alternating context-free grammars (ACFGs).
17 citations
TL;DR: This paper applies the genetic algorithm to a difficult machine learning problem, viz., to learn the description of pushdown automata to accept a context-free language (CFL), given legal and illegal sentences of the language.
Abstract: Genetic algorithms (GAs) are a class of probabilistic optimization algorithms which utilize ideas from natural genetics. In this paper, we apply the genetic algorithm to a difficult machine learning problem, viz., to learn the description of pushdown automata (PDA) to accept a context-free language (CFL), given legal and illegal sentences of the language. Previous work has involved the use of GAs in learning descriptions for finite state machines for accepting regular languages. CFLs are known to properly include regular languages, and hence, the learning problem addressed here is of a greater complexity. The ability to accept context free languages can be applied to a number of practical problems like text processing, speech recognition, etc.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
12 citations
06 Apr 1992
TL;DR: Guest-host electrooptical displays including a mixture of one or more of the compounds with a suitable pleochroic dye exhibit much improved constrast and low driving voltage while eliminating the need for polarizers and excessive dye additions.
Abstract: A simulation ‘free of cost’ of polynomially ambiguity bounded AuxPDAs by unambiguous ones is given. From this it follows that context free languages (CFLs) of polynomial ambiguity can be recognized as efficiently by unambiguous auxiliary pushdown automata (AuxPDAs) as unambiguous CFLs (UCFLs). Furthermore, a first nontrivial upper bound for a circuit class defined by Lange and its closure under complementation are indicated. Finally, normal forms for AuxPDAs are investigated; inter alia it is shown that several kinds of AuxPDAs can be made oblivious, i.e., the movements of all heads are independent from the input.
9 citations
01 Jan 1992
9 citations
TL;DR: Optimization of a two-level microprogrammed automaton is considered, grouping the automaton states into equivalence classes with special encoding based on equivalent transformation of the Automaton.
Abstract: Optimization of a two-level microprogrammed automaton is considered. The optimization method is based on equivalent transformation of the automaton, grouping the automaton states into equivalence classes with special encoding.
8 citations
TL;DR: The equivalence problem for nondeterministic context-free program schemes is unsolvable and the Landweber-Staiger-Wagner hierarchy is extended to pushdown infinite tree automata.
Abstract: We introduce various types of top-down pushdown infinite tree automata. We extend the Landweber-Staiger-Wagner hierarchy to pushdown infinite tree automata. We prove that the extension of Kleene’s theorem to pushdown infinite tree automata is not possible. We characterize recognizable (i.e. regular) infinite trees and extend Eilenberg’s theorem to ω-tree pushdown automata. We give some characterizations of infinite computations of nondeterministic context-free program schemes. We show that the equivalence problem for nondeterministic context-free program schemes is unsolvable.
4 citations
TL;DR: The semiring structure gives a new proof that the types reset-pushdown and one-counter are real-time types and allows the construction of the functional composition of a pushdown transduction and a finite transducer mapping.
4 citations
Proceedings Article•
26 Feb 1992
TL;DR: Pushdown automata on infinite trees with empty stack as the accepting condition (ω-EPDTA) is considered and a Kleene-Closure theorem and a single exponential time algorithm for checking emptiness are provided.
TL;DR: This note shows that several interesting properties of context-free derivations can be characterized by using homomorphic images of left Szilard languages.
Abstract: This note shows that several interesting properties of context-free derivations can be characterized by using homomorphic images of left Szilard languages.
26 Feb 1992
TL;DR: In this article, the authors considered pushdown automata on infinite trees with empty stack as the accepting condition (ω-EPDTA) and provided a relationship to other Pushdown Automata on finite trees, a Kleene-Closure theorem and a single exponential time algorithm for checking emptiness.
Abstract: In this paper we consider Pushdown automata on infinite trees with empty stack as the accepting condition (ω-EPDTA) We provide the following regarding ω-EPDTA (a) its a relationship to other Pushdown automata on infinite trees, (b) a Kleene-Closure theorem and (c) a single exponential time algorithm for checking emptiness We also discuss the relevance of the results presented here to modelchecking