A decision method for the equivalence of some non-real-time deterministic pushdown automata

  • Authors:

  • Esko Ukkonen

  • Affiliations:

  • -

  • Venue:
  • STOC '80 Proceedings of the twelfth annual ACM symposium on Theory of computing
  • Year:
  • 1980

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Abstract

A generalization of the alternate stacking procedure of Valiant for deciding the equivalence of some deterministic pushdown automata (dpda) is introduced. To analyze the power of the generalized procedure we define a subclass of dpda's, called the proper dpda's. This class properly contains the non-singular dpda's and the real time strict dpda's, and the corresponding class of languages properly contains the real time strict deterministic languages. The equivalence problem for proper automata is reducible to the problem of deciding whether or not an automaton is proper. The main result of the paper is that the generalized procedure yields an equivalence test for proper dpda's, at least one of which is also a finite-turn machine.