Topic
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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22 Jun 1987
5 citations
05 Mar 2012
TL;DR: The case of multitape pushdown automata, NPDAs, multitape Turing machines, and other multitape models are investigated, finding a weakly k-synchronized automaton such that L(M′)=L(M)?
Abstract: Given an n-tape automaton M with a one-way read-only head per tape which is delimited by an end marker $ and a nonnegative integer k, we say that M is weakly k-synchronized if for every n-tuple x=(x1, …, xn) that is accepted, there is an accepting computation on x such that no pair of input heads, neither of which is on $, are more than k tape cells apart at any time during the computation. When a head reaches the marker, it can no longer move. As usual, an n-tuple x=(x1, …, xn) is accepted if M eventually reaches the configuration where all n heads are on $ in an accepting state. We look at the following problems: (1) Given an n-tape automaton M, is it weakly k-synchronized for a given k (for some k)? and (2) Given an n-tape automaton M, does there exist a weakly k-synchronized automaton for a given k (for some k) M′ such that L(M′)=L(M)? In an earlier paper [1], we studied the case of multitape finite automata (NFAs). Here, we investigate the case of multitape pushdown automata (NPDAs), multitape Turing machines, and other multitape models. The results that we obtain contrast those of the earlier results and involve some rather intricate constructions.
5 citations
01 May 1990
TL;DR: The results provide further evidence for the general observation that the latter feature provides inherent exponential power, in both upper and lower bound senses, regardless of whether or not the two former features are also present.
5 citations
TL;DR: It is proved that reachability relations of tpda are expressible in linear arithmetic, a rich logic generalising Presburger arithmetic and rational arithmetic.
5 citations
TL;DR: It is shown that thefamily of languages generable by PPA having uniform output length is the homomorphic closure of the family of languages acceptable by P PA.
Abstract: The properties of Probabilistic Pushdown Automata (PPA) are examined. First PPA is defined, various basic properties of it are derived, and several more restrictive types are considered. Then, the families of random languages acceptable and generable by various types of PPA, as well as the families of languages acceptable and generable by various types of PPA with cut-point, are studied. The relationships among these families are also examined, and many interesting results are obtained. Among them, it is shown that the family of languages generable by PPA having uniform output length is the homomorphic closure of the family of languages acceptable by PPA.
5 citations