[comp.theory] stack automata. clarification.

harel@wisdom.weizmann.ac.IL (David Harel) (07/02/90)

   Regarding our posting of Jun 25, we would like to clarify the kinds
of automata we are talking about. They are one-way stack automata (in
contrast to the two-way automata defined in Hopcroft and Ullman, p. 381).
In other words, they are pda's that can travel up and down the stack
(but only one-way along the input), looking and contemplating, but making
changes only at the top. Thus, Hopcroft and Ullman have no results
relevant to our results and questions.