Control Words of String Rewriting P Systems

P systems with controlled computations have been introduced and investigated in the recent past, by assigning labels to the rules in the regions of the P system and guiding the computations by control words. Here we consider string rewriting cell-like transition P system with label assigned rules working in acceptor mode and compare the obtained family of languages of control words over the rule labels with certain well-known language families. An application to chain code picture generation is also pointed out

Membrane Systems Working in Generating and Accepting Modes: Expressiveness and Encodings

Abstract. Membrane systems can be seen either as generators or as acceptors of multiset languages. In this paper we compare the expressive power of membrane systems working in accepting mode with that of membrane systems working in generating mode. Features like determinism, presence of promoters and of cooperative rules are considered. The comparison between some of the considered classes of membrane systems is carried out by defining encodings of one class into another.

Multiset Patterns and Their Application to Dynamic Causalities in Membrane Systems.

In this paper we investigate dynamic causalities in membrane systems by proposing the concept of ``predictor'', originally defined in the context of Ehrenfeucht and Rozemberg's reaction systems. The goal is to characterize sufficient conditions for the presence of a molecule of interest in the configuration of a P system after a given number of evolution steps (independently from the non-deterministic choices taken). Such conditions can be used to study causal relationships between molecules. To achieve our goal, we introduce the new concept of ``multiset pattern'' representing a logical formula on multisets. A predictor can be expressed as a pattern characterizing the initial multisets that will surely lead (sufficient condition) to the presence of the molecule of interest after the given number of evolution steps. We define also an operator that computes such a predictor