@article {, title = {On the branching complexity of P systems}, journal = {Fundamenta Informaticae}, volume = {73}, year = {2006}, pages = {27-36}, publisher = {IOS Press}, address = {Amsterdam, Holanda}, abstract = {We consider two complexity parameters related to the graph of reachable configurations of a given P system, namely the outdegree as a measure of the degree of non-determinism, and the indegree as a measure of the degree of confluence. These parameters can be defined for both the generative and the accepting mode of using a P system. We investigate here these parameters in what concerns hierarchies and decidability issues. We prove that all hierarchies have only two levels and that all considered decidability problems have a negative answer. }, keywords = {decidability, descriptional complexity, Membrane computing, non-determinism}, url = {http://portal.acm.org/citation.cfm?id=1231163}, author = {Gabriel Ciobanu and Gheorghe Paun and Mario J. P{\'e}rez-Jim{\'e}nez} }