Showing papers on "Pushdown automaton published in 1989"
TL;DR: It is shown that small numbers of “role switches” in two- person pebbling can be eliminated and a general result that shows closure under complementation of classes defined by semi-unbounded fan-in circuits is shown.
Abstract: Following the recent independent proofs of Immerman [SIAM J. Comput., 17 (1988), pp. 935–938] and Szelepcsenyi [Bull. European Assoc. Theoret. Comput. Sci., 33 (1987), pp. 96–100] that nondeterministic space-bounded complexity classes are closed under complementation, two further applications of the inductive counting technique are developed. First, an errorless probabilistic algorithm for the undirected graph s-t connectivity problem that runs in $O(\log n)$ space and polynomial expected time is given. Then it is shown that the class LOGCFL is closed under complementation. The latter is a special case of a general result that shows closure under complementation of classes defined by semi-unbounded fan-in circuits (or, equivalently, nondeterministic auxiliary pushdown automata or tree-size bounded alternating Turing machines). As one consequence, it is shown that small numbers of “role switches” in two-person pebbling can be eliminated.
157 citations
Proceedings Article•
01 Jan 1989TL;DR: A higher order single layer recursive network easily learns to simulate a deterministic finite state machine and recognize regular grammars and can be interpreted as a neural net pushdown automata.
Abstract: A higher order single layer recursive network easily learns to simulate a deterministic finite state machine and recognize regular grammars. When an enhanced version of this neural net state machine is connected through a common error term to an external analog stack memory, the combination can be interpreted as a neural net pushdown automata. The neural net finite state machine is given the primitives, push and POP, and is able to read the top of the stack. Through a gradient descent learning rule derived from the common error function, the hybrid network learns to effectively use the stack actions to manipulate the stack memory and to learn simple contextfree grammars.
130 citations
Book•
11 Jan 1989TL;DR: This book discusses Grammatical Basis of Language Translation, Foundations of Recursive Function Theory, and the Scope of Primitive Recursive functions in Partial Recursive Functions.
Abstract: Preliminaries Review of Set Theory Grammatical Basis of Language Translation Historical Background Preview of the Remaining Text Chapter Review Problems Finite Automata and Regular Languages Lexical Analysis Deterministic Finite Automata The Limits of Deterministic Finite Automata Nondeterministic Finite Automata Regular Grammars Regular Expressions Closing Comments Chapter Review Problems Pushdown Automata and Context-Free Languages Pushdown Automata Context-Free Grammars The Limits of Pushdown Automata LL(k) Parsers LR(k) Parsers Turing Machines and Phase-Structure Languages Turing Machines Modular Construction of Turing Machines Turing Machines as Language Accepters Turing-Acceptable Languages Beyond Phrase-Structure Languages Closing Comments Chapter Review Problems Computability Foundations of Recursive Function Theory The Scope of Primitive Recursive Functions Partial Recursive Functions The Power of Programming Languages Closing Comments Chapter Review Problems Complexity Computations The Complexity of Algorithms The Complexity of Problems Time Complexity of Language Recognition Problems Time Complexity of Nondeterministic Machines Closing Comments Chapter Review Problems Appendices A More About Constructing LR(1) Parse Tables B More About Ackerman's Function C Some Important Unsolvable Problems D On the Complexity of the String Comparison Problem E A Sampling of NP Problems Additional Reading 0805301437T04062001
78 citations
01 Feb 1989
TL;DR: These algorithms are the first which are provably effective for these problems, in the absence of a “reset,” and probabilistic algorithms for permutation automata which do not require a teacher to supply counterexamples are presented.
Abstract: We present new algorithms for inferring an unknown finite-state automaton from its input/output behavior in the absence of a means of resetting the machine to a start state. A key technique used is inference of a homing sequence for the unknown automaton.Our inference procedures experiment with the unknown machine, and from time to time require a teacher to supply counterexamples to incorrect conjectures about the structure of the unknown automaton. In this setting, we describe a learning algorithm which, with probability 1-d, outputs a correct description of the unknown machine in time polynomial in the automaton's size, the length of the longest counterexample, and log (1/d). We present an analogous algorithm which makes use of a diversity-based representation of the finite-state system. Our algorithms are the first which are provably effective for these problems, in the absence of a “reset.”We also present probabilistic algorithms for permutation automata which do not require a teacher to supply counterexamples. For inferring a permutation automaton of diversity D, we improve the best previous time bound by roughly a factor of D3/logD.
77 citations
26 Jun 1989
TL;DR: A novel formalism is presented for Earley-like parsers that accommodates the simulation of non-deterministic pushdown automata and is applied to non-Deterministic LR-parsers for RTN grammars.
Abstract: A novel formalism is presented for Earley-like parsers. It accommodates the simulation of non-deterministic pushdown automata. In particular, the theory is applied to non-deterministic LR-parsers for RTN grammars.
36 citations
TL;DR: To every input string of a two-way automaton one associates a quadruple of partial functions between the states, and this quadruple describes the behavior of the automaton on that input, and can also be used to formulate acceptance, or notions like the crossing sequence.
26 citations
TL;DR: It is shown that the class of alternating context-free languages is equal to theclass of languages accepted by alternating pushdown automata.
22 citations
TL;DR: In this paper, it was shown that the most usual finiteness conditions on a subgroup of a finitely generated group all have equivalent formulations in terms of formal language theory.
Abstract: We show in this article that the most usual finiteness conditions on a subgroup of a finitely generated group all have equivalent formulations in terms of formal language theory. This correspondence gives simple proofs of various theorems concerning intersections of subgroups and the preservation of finiteness conditions in a uniform manner. We then establish easily the theorems of Greibach and of Griffiths by considering free reductions of languages that describe the computations of pushdown automata in one case and of Turing machines in the other, thus making clear that they are essentially the same.
22 citations
TL;DR: A new direct branching algorithm is presented for checking the equivalence of deterministic pushdown transducers, one of whose associated deterministicpushdown automata (DPDAs) is real-time strict.
12 citations
TL;DR: In this paper, an alternating auxiliary pushdown hierarchy is defined by extending the machine model of the Logarithmic Alternation Hierarchy by a pushdown store while keeping a polynomial time bound.
Abstract: An alternating auxiliary pushdown hierarchy is defined by extending the machine model of the Logarithmic Alternation Hierarchy by a pushdown store while keeping a polynomial time bound. Although recently it was proven by Borodin et al. that the class of languages accepted by nondeterministic logarithmic space bounded auxiliary pushdown automata with a polynomial time bound is closed under complement [Bo et al], it is shown that, surprisingly, the further levels of this alternating auxiliary pushdown hierarchy coincide level by level with the Polynomial Hierarchy. Furthermore, it is shown that PSPACE can be characterized by simultaneously logarithmic space and polynomial time bounded auxiliary pushdown automata with unbounded alternation.
10 citations
TL;DR: It is shown that deterministic two-way checking stack automata have the same power as deterministicTwo-way two- way two-head finite automata.
Abstract: It is well known that nondeterministic two-way checking stack automata recognize NSPACE( n ). We show that deterministic two-way checking stack automata have the same power as deterministic two-way two-head finite automata. The easy proof is based on the closure under inverse deterministic two-way GSM mappings of the deterministic two-way two-head finite automaton languages.
TL;DR: The upper bound on the order of a locally testable deterministic automaton is at most n4 + 1, where n is the number of states of the automaton.
Abstract: A locally testable language is a language with the property that for some nonnegative integer k, called the order of locality, whether or not a word w is in the language depends on (1) the prefix and suffix of w of length k, and (2) the set of intermediate substrings of w of length k + 1, without regard to the order in which these substrings occur. The local testability problem is, given a deterministic finite automaton, to decide whether it accepts a locally testable language or not. Recently, we introduced the first polynomial time algorithm for the local testability problem based on a simple characterization of locally testable deterministic automata. This paper investigates the upper bound on the order of locally testable automata. It shows that the order of a locally testable deterministic automaton is at most n4 + 1, where n is the number of states of the automaton.
16 Feb 1989
TL;DR: This paper considers the pushdown reversal complexity of auxiliary pushdown automata, and shows that pushdown reversals provide a uniform measure for the characterization of awide range of complexity classes, located between L and P.
Abstract: Auxiliary pushdown automata have been proven to be a useful tool for the characterization of complexity classes. In this paper we consider the pushdown reversal complexity of these machines, and show that especially in connection with a simultaneous space bound, pushdown reversals provide a uniform measure for the characterization of awide range of complexity classes, located between L and P. It is shown that classes defined by reversal bounds are included in those of restricted pushdown height.
DOI•
21 Feb 1989TL;DR: This paper settled James Peterson's conjecture that any significant extension of the Petri net model tends to be equivalent to a Turing machine negatively.
Abstract: A new class of "concurrent automata" is constructed. These automata are extensions of pushdown automata and Petri nets. They lie properly between ordinary Petri nets and Turing machines. In the September 1977 issue of Computing survey James Peterson states that "Any significant extension of the Petri net model tends to be equivalent to a Turing machine". This paper settled his conjecture negatively. The formal languages that are accepted/reconized by this automata lie properly between context free languages and context sensitive languages.
TL;DR: The factors that make it difficult to generalize pushdown automata for one-dimensional strings to two-dimensional arrays are investigated and solved, and two- dimensional pushdown array automata (PDAA) are constructed.
Abstract: We investigate the factors that make it difficult to generalize pushdown automata for one-dimensional strings to two-dimensional arrays. Then we resolve the problems and construct two-dimensional pushdown array automata (PDAA). The relationship between isometric context-free array languages and pushdown array automata is established. Several examples of array automata are presented, and a pushdown array automaton is tested on VAX8650/VMS using PASCAL.
Journal Article•
TL;DR: Introduction de deuse de deux mesures de non determinisme pour la classification des langages CF et trois familles de langage CF sont consideres.
Abstract: Introduction de deux mesures de non determinisme pour la classification des langages CF. Trois familles de langages CF sont consideres
TL;DR: It is shown that the bounded cellular automaton can recognize in nearly half the time the class of languages which can be recognized in real time.
Abstract: With the progress of VLSI technology, researchers are more interested in parallel computation. For example, discussions are made on the parallel processings such as the recognition of language, sorting, matrix computation and graph processing, using the systolic array, the iterative array, and the bounded cellular automaton. It was shown in a previous paper that the bounded cellular automaton is properly faster in the recognition of language than the systolic array, i.e., one-way cellular automaton. This paper is a continuation of that previous paper, and shows that the bounded cellular automaton can recognize in nearly half the time the class of languages which can be recognized in real time.