Showing papers on "Pushdown automaton published in 1983"
TL;DR: Topdown pushdown tree automata are defined and shown to be equivalent to restricted PDTA's, whose stack is linear: this both yields a more operational way of recognizing context-free tree languages and connects them with the class of indexed languages.
Abstract: We define topdown pushdown tree automata (PDTA's) which extend the usual string pushdown automata by allowing trees instead of strings in both the input and the stack. We prove that PDTA's recognize the class of context-free tree languages. (Quasi)realtime and deterministic PDTA's accept the classes of Greibach and deterministic tree languages, respectively. Finally, PDTA's are shown to be equivalent to restricted PDTA's, whose stack is linear: this both yields a more operational way of recognizing context-free tree languages and connects them with the class of indexed languages.
82 citations
01 Dec 1983
TL;DR: It is shown that alternation corresponds to one more iteration of pushdowns, and nondeterministic 2-way and multi-head iterated pushdown automata characterize deterministic iterated exponential time complexity classes.
Abstract: An iterated pushdown is a pushdown of pushdowns of ... of pushdowns. An iterated exponential function is 2 to the 2 to the ... to the 2 to some polynomial. The main result is that nondeterministic 2-way and multi-head iterated pushdown automata characterize deterministic iterated exponential time complexity classes. This is proved by investigating both nondeterministic and alternating auxiliary iterated pushdown automata, for which similar characterization results are given. In particular it is shown that alternation corresponds to one more iteration of pushdowns. These results are applied to the 1-way iterated pushdown automata: (1) they form a proper hierarchy with respect to the number of iterations, (2) their emptiness problem is complete in deterministic iterated exponential time.
64 citations
TL;DR: It is shown that k + 1 heads are better than k for one-way multihead pushdown (resp. stack) automata if they do not have endmarkers on the input tape and accept by final state with at least one input head at the right end of the input string.
10 citations
9 citations
6 citations
TL;DR: An algorithm simulating 2dpda(k)‘s in O(r) time and space, where r is the number of reachable surface configurations, is designed, to obtain a similar result for two-way nondeterministic pushdown automata.
5 citations
TL;DR: It seems that there are subclasses of pushdown acceptors which have a decidable ambiguity problem but an undecidable inherent ambiguity problem, and these classes are the first known to exhibit this property.
3 citations
TL;DR: The family of stack uniform strict deterministic languages can be characterized by a grammar family because the grammar is required to be in a special form, but the construction is more natural than previously known constructions.
1 citations
TL;DR: A new type of automaton on a two-dimensional tape is introduced, which decides acceptance or rejection of an input tape x by first scanning the tape x from various sides with parallel/sequential array readers, and by then scanning the pair of the halting state configurations generated by these array readers with a multitape finite automaton.
01 Jan 1983
TL;DR: A finite semi-Markov decision process is studied to maximize the expected average reward and convergence results are stated in the form of theorems and some examples are given.
Abstract: A finite semi-Markov decision process is studied to maximize the expected average reward. The semi-Markov kernel of the process depends on an unknown parameter taking values in a subset [a, b] of ℝS. A controller modelled as a learning automaton updates sequentially the probabilities of generating decisions based on the observed decisions, states, and jump times. Convergence results are stated in the form of theorems and some examples are given.