%0 Journal Article
%T A Reduction of Finitely Expandable Deep Pushdown Automata
%A Dvořáková, Lucie
%A Meduna, Alexander
%J Schedae Informaticae
%V 2017
%R 10.4467/20838476SI.17.005.8151
%N Volume 26
%P 61-68
%K Finite Expandability, Reduction, Non- Input Pushdown Symbols, Deep Pushown Automata
%@ 1732-3916
%D 2018
%U https://ejournals.eu/en/journal/schedae-informaticae/article/a-reduction-of-finitely-expandable-deep-pushdown-automata
%X 
	For a positive integer n, n-expandable deep pushdown automata always contain no more than n occurrences of non-input symbols in their pushdowns during any computation. As its main result, the present paper demonstrates that these automata are as powerful as the same automata with only two non-input pushdown symbols - $ and #, where # always appears solely as the pushdown bottom. The paper demonstrates an infinite hierarchy of language families that follows from this main result. The paper also points out that if # is the only non-input symbol in these automata, then they characterize the family of regular languages. In its conclusion, the paper suggests open problems and topics for the future investigation.