On Catalytic P Systems with One Catalyst

In this paper we address the possibility of studying the computational capabilities of catalytic P systems with one catalyst by the means of iterated finite state transducers. We also give a normal form for catalytic P systems

Further Results on P Systems with Promoters/Inhibitors

The paper gives several results regarding P systems with non-cooperative rules and promoters/inhibitors at the level of rules. For the class of P systems using inhibitors, generating families of sets of vectors of numbers, the equivalence with the family of Parikh sets of ET0L languages is presented. In case of P systems with non- cooperative promoted rules even if an upper bound was not given, the inclusion of the family PsET0L was proved. Moreover, a characterization of such systems by means of a particular form of random context grammars, therefore a sequential formal device, is proposed

Parallel Graph Rewriting Systems

In this paper we introduce a new theoretical paradigm, called PGR systems, which can be used to model in a discrete manner some natural phenomena occurring in-vivo/in-vitro en- vironments. PGR systems make use of graphs to describe the spatial structure of space of individuals, while the system dynamics caused by the movement/interaction of individuals is captured by the parallel applications of some graph rewriting rules. In this frame, an il- lustrative example is studied and based on it, an eloquent comparison between the abstract rewriting machines and PGR systems is done. Several further ideas to overcome the global computational effort needed for simulations, but still maintaining the overall ability for mod- eling are finally proposed

On P Systems with Promoters/Inhibitors

This article shows how the computational universality can be reached by using P systems with object rewriting context-free rules, promot- ers/inhibitors and one catalyst. Both generative and accepting cases are stud- ied. Some examples that illustrate the theoretical issues are also presented

Several Applications of Spiking Neural P Systems

In this paper we investigate some applications of Spiking Neural P Systems regarding their capability to solve some classical computer science problems. In this respect it is studied the versatility of such systems to simulate a well known parallel computational model, namely the Boolean circuits. In addition, another notorious application - the sorting - is considered within this framework

(Ultimately Confluent) Parallel Multiset-Rewriting Systems with Context

The aim of this paper is to study the power of parallel multiset- rewriting systems with permitting context (or P systems with non-cooperative rules with promoters). The main result obtained is that if we use promoters of weight two, then the system is universal. Moreover, the construction satis¯es a special property we de¯ne: it is ulti- mately con°uent. This means that if the system allows at least one halting computation, then its ¯nal con¯guration is reachable from any reachable con- ¯guration

P Systems with Adjoining Controlled Communication Rules

This paper proposes a new model of P systems where the rules are activated by objects present in the neighboring regions. We obtain the computational completeness considering only two membranes, external inhibitors and carriers. Leaving the carriers apart we obtain equality with ET0L systems in terms of number sets

Scenario Based P Systems

In this paper we de ne and study Scenario Based P Systems, a model of computation inspired by the metabolic pathways and networks. Starting from the classical de nition of P systems with symbol objects and multiset rewriting rules, we de ne regular expressions able to capture the causal dependencies among di erent executions of the rules. The results show the computational power of this model

Computing Using Signals: From Cells to P Systems

In cell biology one of the fundamental topic is the study of how biological signals are managed by cells. Signals can arise from inside the cell or from the external environment and the correct answer to certain signals is essential for bacteria to survive in a certain environment. Starting from these biological motivations we consider a model of P systems where the computa- tion is controlled by signals which move across the regions. In particular, we consider Signals-Based P systems where the symbol-objects cannot be moved and the rules can be activated/inactivated using a ¯nite number of signals (signal-promoters) moved across the membranes; di®erently from standard P systems using promoters, in our case promoters cannot be created during the computation. After discussing the biological motivations we show how this model becomes universal when it uses one catalyst, and a bounded number of signal-promoters

Membrane Systems with External Control

We consider the idea of controlling the evolution of a membrane system. In particular, we investigate a model of membrane systems using promoted rules, where a string of promoters (called the control string) “travels” through the regions, activating the rules of the system. This control string is present in the skin region at the beginning of the computation – one can interpret that it has been inserted in the system before starting the computation – and it is “consumed”, symbol by symbol, while traveling through the system. In this way, the inserted string drives the computation of the membrane system by controlling the activation of evolution rules. When the control string is entirely consumed and no rule can be applied anymore, then the system halts – this corresponds to a successful computation. The number of objects present in the output region is the result of such a computation. In this way, using a set of control strings (a control program), one generates a set of numbers. We also consider a more restrictive definition of a successful computation, and then study the corresponding model. In this paper we investigate the influence of the structure of control programs on the generative power. We demonstrate that different structures yield generative powers ranging from finite to recursively enumerable number sets. In determining the way that the control string moves through the regions, we consider two possible “strategies of traveling”, and prove that they are similar as far as the generative power is concerned