C. Ferretti, G. Mauri, Gh. Paun, C. Zandron
On three variants of rewriting P systems.

Abstract

We continue here the study of P systems with string-objects processed by rewriting rules, by investigating some questions which are classic in formal language theory: leftmost derivation, conditional use of rules (permitting and forbiddingconditions), relationships with language families in Chomsky and Lindenmayer hierarchies.