Labelled graph rules in P systems

P systems with graph productions were introduced by Freund in 2004. It was shown that such a variant of P system can generate any recursively enumerable language of weakly connected graphs. In this paper, we consider such P systems where the input is any connected graph and each graph production is labelled over an alphabet. We name the system as Process Guided P System where the computation is guided by a string over the set of labels. The set of all strings over the label alphabet which results in the halting computation of the system forms a guiding language of the system. We compare such guiding languages with Chomsky hierarchy. Two direct applications of this variant are also given.