On power of P Systems using sequential and parallel rewriting

A new class of distributed computing models inspired from biology, that of P Systems, was recently introduced by Gh. paun. Several variants of P Syste ms were already shown to be computationally universal, equal in power to Tu ring Machines. We investigate in this paper the power of computability of P Systems based on rewriting, with cooperation, priorities and external outp ut. It is established that rewriting P Systems with priorities and two memb ranes is computationally universal, thereby making an improvement in the ex isting result that RE subset of or equal to RP3(Pri). We give a new model i n P Systems stressing the importance of parallelism. The power of computabi lity of such models is investigated by comparing them with classic mechanis ms in L-Systems: TOL, EOL and ETOL Systems.