<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="6.x">Drupal-Biblio</source-app><ref-type>13</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Gabriel Ciobanu</style></author><author><style face="normal" font="default" size="100%">Gheorghe Paun</style></author><author><style face="normal" font="default" size="100%">Mario J. Pérez-Jiménez</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">On the branching complexity of P systems</style></title><secondary-title><style face="normal" font="default" size="100%">Fundamenta Informaticae</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">decidability</style></keyword><keyword><style  face="normal" font="default" size="100%">descriptional complexity</style></keyword><keyword><style  face="normal" font="default" size="100%">Membrane computing</style></keyword><keyword><style  face="normal" font="default" size="100%">non-determinism</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2006</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://portal.acm.org/citation.cfm?id=1231163</style></url></web-urls></urls><publisher><style face="normal" font="default" size="100%">IOS Press</style></publisher><pub-location><style face="normal" font="default" size="100%">Amsterdam, Holanda</style></pub-location><volume><style face="normal" font="default" size="100%">73</style></volume><pages><style face="normal" font="default" size="100%">27-36</style></pages><abstract><style face="normal" font="default" size="100%">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. 

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