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Pushdown automaton

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


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Journal ArticleDOI
TL;DR: This work presents a second-order logic with the same expressive power as Buchi or Muller pushdown automata for infinite words and extends fundamental logical characterizations of Buchi, Elgot, Trakhtenbrot for regular languages of finite and infinite words to ω-context-free languages.
Abstract: Context-free languages of infinite words have recently found increasing interest. Here, we will present a second-order logic with the same expressive power as Buchi or Muller pushdown automata for infinite words. This extends fundamental logical characterizations of Buchi, Elgot, Trakhtenbrot for regular languages of finite and infinite words and a more recent logical characterization of Lautemann, Schwentick and Therien for context-free languages of finite words to ω-context-free languages. For our argument, we will investigate Greibach normal forms of ω-context-free grammars as well as a new type of Buchi pushdown automata which can alter their stack by at most one element and without ϵ-transitions. We show that they suffice to accept all ω-context-free languages. This enables us to use similar results recently developed for infinite nested words.

6 citations

Journal ArticleDOI
TL;DR: The relation between reversals and alternation is studied in two simple models of computation: the 2-counter machine with a one-way input tape and the one- way pushdown automaton whose pushdown store makes only one reversal (1-reversal PDA).
Abstract: The relation between reversals and alternation is studied in two simple models of computation: the 2-counter machine with a one-way input tape whose counters make only one reversal (1-reversal 2CM) and the one-way pushdown automaton whose pushdown store makes only one reversal (1-reversal PDA). The following is shown: (a) alternating 1-reversal 2CM’s accept all recursively enumerable languages; (b) alternating 1-reversal PDA’s accept exactly the languages accepted by exponential time-bounded deterministic TM’s. The first improves on the known result that alternating 1-reversal 4CM’s accept all recursively enumerable languages. The second improves an earlier result that alternating PDA’s with no restrictions on reversals accept exactly the exponential-time languages.

6 citations

Journal ArticleDOI
TL;DR: On purpose to reduce the size of this array, the compressed configurations are introduced which will record terminators of configurati.ons and use recorded values to speed up +he automaton.

6 citations

Book ChapterDOI
30 Jun 2011
TL;DR: This paper proposes a method to extend the approach to pushdown systems that can encode either a stack data structure or the call stack that is based on context-free grammar algorithms, and relies on combinatorial techniques to guarantee the uniformity of generated traces.
Abstract: Developing efficient and automatic testing techniques is one of the major challenges facing the software validation community. Recent work by Denise and al. (in MBT'08 proceedings) shows how to draw traces uniformly at random in large systems modeled by finite automata for testing purposes. Since finite automata are strong abstractions of systems, many generated test cases following this approach may be un-concretizable, i.e., do not correspond to any concrete execution of the system under test. In this paper, we propose to tackle this problem by extending the approach to pushdown systems that can encode either a stack data structure or the call stack. The method is based on context-free grammar algorithms, and relies on combinatorial techniques to guarantee the uniformity of generated traces.

6 citations

Posted Content
TL;DR: The notion of many-one CFL reducibility was introduced in this paper, which is a natural restriction of NP-reducibility and conducts a ground work to formulate a coherent framework for further expositions.
Abstract: To expand a fundamental theory of context-free languages, we equip nondeterministic one-way pushdown automata with additional oracle mechanisms, which naturally induce various nondeterministic reducibilities among formal languages. As a natural restriction of NP-reducibility, we introduce a notion of many-one CFL reducibility and conduct a ground work to formulate a coherent framework for further expositions. Two more powerful reducibilities--bounded truth-table and Turing CFL-reducibilities--are also discussed in comparison. The Turing CFL-reducibility, in particular, helps us introduce an exquisite hierarchy, called the CFL hierarchy, built over the family CFL of context-free languages. For each level of this hierarchy, its basic structural properties are proven and three alternative characterizations are presented. The second level is not included in NC(2) unless NP= NC(2). The first and second levels of the hierarchy are different. The rest of the hierarchy (more strongly, the Boolean hierarchy built over each level of the hierarchy) is also infinite unless the polynomial hierarchy over NP collapses. This follows from a characterization of the Boolean hierarchy over the k-th level of the polynomial hierarchy in terms of the Boolean hierarchy over the k+1st level of the CFL hierarchy using log-space many-one reductions. Similarly, the complexity class Theta(k) is related to the closure of the k-th level of the CFL hierarchy under log-space truth-table reductions. We also argue that the CFL hierarchy coincides with a hierarchy over CFL built by application of many-one CFL-reductions. We show that BPCFL--a bounded-error probabilistic version of CFL--is not included in CFL even in the presence of advice. Employing a known circuit lower bound and a switching lemma, we exhibit a relativized world where BPCFL is not located within the second level of the CFL hierarchy.

6 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202314
202234
202129
202052
201947
201834