On the generative power of regular pattern grammars

Abstract

It is shown that for every recursively enumerable language L $$ \subseteq $$ ?* there exists a selective substitution grammar with a regular selector over a binary alphabet that generates L¢5, where ¢??. By requiring additional structural properties of the (already simple) selectors the language generating power is reduced in such a way that the resulting class lies strictly in between the family of EOL languages and the family of context-sensitive languages. For this class of languages some decision problems and normal forms are considered.