Affiliations: Institute of Mathematics of the Romanian Academy, PO Box 1 – 764, 70700 Bucureşti, Romania. e-mail: [email protected] | Department of Computer Science, University of Western Ontario, N6A 5B7 London, Ontario, Canada e-mail: [email protected]
Note: [] Address for correspondence: Institute of Mathematics of the Romanian Academy, PO Box 1 – 764, 70700 Bucureşti, Romania
Note: [] Address for correspondence: Department of Computer Science, University of Western Ontario, N6A 5B7 London, Ontario, Canada
Abstract: The P systems were recently introduced as distributed parallel computing models of a biochemical type. Multisets of objects are placed in a hierarchical structure of membranes and they evolve according to given rules, which are applied in a synchronous manner: at each step, all objects which can evolve, from all membranes, must evolve. We consider here the case when this restriction is removed. As expected, unsynchronized systems (even using catalysts) are weaker than the synchronized ones, providing that no priority relation among rules is considered. The power of P systems is not diminished when a priority is used and, moreover, the catalysts can change their states, among two possible states for each catalyst.
Keywords: P systems, Synchronization, Recursively enumerable languages, Matrix grammars
