On stateless deterministic restarting automata

Abstract

The transitions of a stateless automaton do not depend on internal states but solely on the symbols currently scanned by its heads accessing the input or memory. We investigate stateless deterministic restarting automata that, after executing a rewrite step, continue to read their tape before performing a restart. Even the weakest class thus obtained contains the regular languages properly. The relations between different classes of stateless automata as well as between stateless automata and the corresponding types of automata with states are investigated, and it is shown that the language classes defined by the various types of deterministic stateless restarting automata without auxiliary symbols are anti-AFLs that are not even closed under reversal. © Springer-Verlag Berlin Heidelberg 2009.