@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}
}
