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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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TL;DR: It is mainly shown that, for an L-valued context-free grammar, anL-valued Greibach Normal Form can be equivalently constructed.
9 citations
TL;DR: This paper investigates the power of quantum pushdown automata whose stacks are assumed to be implemented as classical devices, and shows that they are strictly more powerful than their classical counterparts under the perfect-soundness condition.
Abstract: One important question for quantum computing is whether a computational gap exists between models that are allowed to use quantum effects and models that are not. Several types of quantum computation models have been proposed, including quantum finite automata and quantum pushdown automata (with a quantum pushdown stack). It has been shown that some quantum computation models are more powerful than their classical counterparts and others are not since quantum computation models are required to obey such restrictions as reversible state transitions. In this paper, we investigate the power of quantum pushdown automata whose stacks are assumed to be implemented as classical devices, and show that they are strictly more powerful than their classical counterparts under the perfect-soundness condition, where perfect-soundness means that an automaton never accepts a word that is not in the language. That is, we show that our model can simulate any probabilistic pushdown automata and also show that there is a non-context-free language which quantum pushdown automata with classical stack operations can recognize with perfect soundness.
9 citations
25 Aug 2014
TL;DR: The reachability of pushdown automata over infinite alphabets was investigated in this article, where it was shown that these machines can be faithfully represented by using only 3r elements of the infinite alphabet, where r is the number of registers.
Abstract: We investigate reachability in pushdown automata over infinite alphabets: machines with finite control, a finite collection of registers and pushdown stack. First we show that, despite the stack’s unbounded storage capacity, in terms of reachability/emptiness these machines can be faithfully represented by using only 3r elements of the infinite alphabet, where r is the number of registers. Moreover, this bound is tight. Next we settle the complexity of the associated reachability/emptiness problems. In contrast to register automata, where differences in register storage policies gave rise to differing complexity bounds, the emptiness problem for pushdown register automata is EXPTIME-complete in all cases. We also provide a solution to the global reachability problem, based on representing pushdown configurations with a special register automaton. Finally, we examine extensions of pushdown storage to higher orders and show that reachability is undecidable already at order 2, unlike in the finite alphabet case.
9 citations
23 Jul 2012
TL;DR: The descriptional cost of converting constant height nondeterministic pushdown automata into equivalent deterministic devices is studied and a double-exponential upper bound for this conversion is shown, together with a super-exp exponential lower bound.
Abstract: We study the descriptional cost of converting constant height nondeterministic pushdown automata into equivalent deterministic devices. We show a double-exponential upper bound for this conversion, together with a super-exponential lower bound.
9 citations
14 Jun 2011
TL;DR: Floyd automata as mentioned in this paper is an equivalent operational formalism for defining FLs, which also permits to extend the class to deal with infinite strings to perform for instance model checking.
Abstract: Operator precedence grammars define a classical Boolean and deterministic context-free family (called Floyd languages or FLs). FLs have been shown to strictly include the well-known visibly pushdown languages, and enjoy the same nice closure properties. We introduce here Floyd automata, an equivalent operational formalism for defining FLs. This also permits to extend the class to deal with infinite strings to perform for instance model checking.
9 citations