(Mem)brane automata

We introduce the notion of a P automaton with marked membranes, a Ppp automaton for short, which is an accepting variant of P systems. The concept is motivated by the theory of P systems, brane calculi, and the traditional concept of automata. In P systems with marked membranes, bio-molecules (proteins) are allowed to move through the membranes and to attach onto or to de-attach from the membranes. The membrane system evolves according to rules which are defined over multisets of proteins and describe the above actions. In addition to these features, the P automaton with marked membranes is able to consume inputs from its environment, i.e. multisets of proteins, which might influence the behaviour of the system. The result of the computation is the set of multiset sequences consumed by the skin membrane, supposing that the Ppp automaton started functioning in the initial configuration and entered a final configuration at halting. We show that any recursively enumerable language can be obtained as the language accepted by a Ppp automaton modulo a simple computable mapping.