scispace - formally typeset
Search or ask a question
Topic

Pushdown automaton

About: Pushdown automaton is a research topic. Over the lifetime, 1868 publications have been published within this topic receiving 35399 citations.


Papers
More filters
Journal ArticleDOI
TL;DR: The existence of pseudoequivalent states permits minimizing the length of the direct structural table of the Moore automaton and thus reduces the number of terms in the system of automaton memory excitation functions.
Abstract: The existence of pseudoequivalent states permits minimizing the length of the direct structural table of the Moore automaton and thus reduces the number of terms in the system of automaton memory excitation functions. Automaton logic optimization requires unique identification of the classes of pseudoequivalent states. Method M1 identifies the classesB i ∈ πga without using additional variables and states. However, the application of this method does not always reduce the DST to the corresponding parameter of the equivalent Mealy automaton. Moreover, forR > R 0 the number of feedback parameters in the Moore automaton is greater than in the equivalent Mealy automaton. Method M2 attains the absolute minimum DST length and the absolute minimum number of feedback variables, which are equal to the corresponding parameters of the equivalent Mealy automaton. Moreover, state encoding can be applied that minimizes the number of terms in the microoperation system. However, M2 requires the introduction of a special code converter and thus involves additional hardware costs.

30 citations

Journal ArticleDOI
TL;DR: In this article, it was shown that a language C is rankable in deterministic polynomial time iffP = P #P #P677, whereP is any of the following six classes of languages: (1) languages accepted by log-time-bounded non-turing machines, (2) languages accept by (uniform) families of unbounded fan-in circuits, (3) languages acceptance by 2-way deterministic pushdown automata, (4) languages accepting by multi-head deterministic finite automata and (5)
Abstract: Ranking is the problem of computing for an input string its lexicographic index in a given (fixed) language. This paper concerns the complexity of ranking. We show that ranking languages accepted by 1-way unambiguous auxiliary pushdown automata operating in polynomial time is inNC (2). We also prove negative results about ranking for several classes of simple languages.C is rankable in deterministic polynomial time iffP=P #P , whereC is any of the following six classes of languages: (1) languages accepted by logtime-bounded nondeterministic Turing machines, (2) languages accepted by (uniform) families of unbounded fan-in circuits of constant depth and polynomial size, (3) languages accepted by 2-way deterministic pushdown automata, (4) languages accepted by multihead deterministic finite automata, (5) languages accepted by 1-way nondeterministic logspace-bounded Turing machines, and (6) finitely ambiguous linear context-free languages.

30 citations

Book ChapterDOI
27 Aug 2006
TL;DR: In this paper, the authors define modular visibly pushdown automata (modular VPA) and show that for the class of languages accepted by such automata, unique minimal modular VPA exist.
Abstract: Boolean programs with recursion are convenient abstractions of sequential imperative programs, and can be represented as recursive state machines (RSMs) or pushdown automata. Motivated by the special structure of RSMs, we define a notion of modular visibly pushdown automata (modular VPA) and show that for the class of languages accepted by such automata, unique minimal modular VPA exist. This yields an efficient approximate minimization theorem that minimizes RSMs to within a factor of k of the minimal RSM, where k is the maximum number of parameters in any module. Using the congruence defined for minimization, we show an active learning algorithm (with a minimally adequate teacher) for context free languages in terms of modular VPAs. We also present an algorithm that constructs complete test suites for Boolean program specifications. Finally, we apply our results on learning and test generation to perform model checking of black-box Boolean programs.

29 citations

Book ChapterDOI
06 Jul 2015
TL;DR: For language classes that are closed under rational transductions, it is shown that the computation of downward closures can be reduced to checking a certain unboundedness property in this paper.
Abstract: The downward closure of a word language is the set of all not necessarily contiguous subwords of its members It is well-known that the downward closure of any language is regular While the downward closure appears to be a powerful abstraction, algorithms for computing a finite automaton for the downward closure of a given language have been established only for few language classes This work presents a simple general method for computing downward closures For language classes that are closed under rational transductions, it is shown that the computation of downward closures can be reduced to checking a certain unboundedness property This result is used to prove that downward closures are computable for i every language class with effectively semilinear Parikh images that are closed under rational transductions, ii matrix languages, and iii indexed languages equivalently, languages accepted by higher-order pushdown automata of orderi¾?2

29 citations

Book ChapterDOI
03 Jul 2007
TL;DR: It is proved that the model checking problem over 2-OVPA models against 2-ovPA specifications is EXPTIME-complete and the automata-theoretic approach is shown to be strictly more expressive than VPA.
Abstract: Visibly Pushdown Automata (VPA) are a special case of pushdown machines where the stack operations are driven by the input. In this paper, we consider VPA with two stacks, namely 2-VPA. These automata introduce a useful model to effectively describe concurrent pushdown systems using a simple communication mechanism between stacks. We show that 2-VPA are strictly more expressive than VPA. Indeed, 2-VPA accept some context-sensitive languages that are not context-free and some context-free languages that are not accepted by any VPA. Nevertheless, the class of languages accepted by 2-VPA is closed under all boolean operations and determinizable in EXPTIME, but does not preserve decidability of emptiness problem. By adding an ordering constraint on stacks (2-OVPA), decidability of emptiness can be recovered (preserving desirable closure properties) and solved in PTIME. Using these properties along with the automata-theoretic approach, we prove that the model checking problem over 2-OVPA models against 2-OVPA specifications is EXPTIME-complete.

29 citations


Network Information
Related Topics (5)
Time complexity
36K papers, 879.5K citations
87% related
Finite-state machine
15.1K papers, 292.9K citations
86% related
Model checking
16.9K papers, 451.6K citations
84% related
Concurrency
13K papers, 347.1K citations
84% related
String (computer science)
19.4K papers, 333.2K citations
83% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202314
202234
202129
202052
201947
201834