Petri net algorithms in the theory of matrix grammars
Acta Informatica
Programmed Grammars and Classes of Formal Languages
Journal of the ACM (JACM)
Membrane computing with external output
Fundamenta Informaticae
P systems with active membranes: attacking NP-complete problems
Journal of Automata, Languages and Combinatorics
On membrane computing based on splicing
Where mathematics, computer science, linguistics and biology meet
Handbook of Formal Languages
Regulated Rewriting in Formal Language Theory
Regulated Rewriting in Formal Language Theory
On P Systems with Active Membranes
UMC '00 Proceedings of the Second International Conference on Unconventional Models of Computation
Computing with Membranes: Attacking NP-Complete Problems
UMC '00 Proceedings of the Second International Conference on Unconventional Models of Computation
Solving NP-Complete Problems Using P Systems with Active Membranes
UMC '00 Proceedings of the Second International Conference on Unconventional Models of Computation
Computing with Membranes
On the power of membrane division in P systems
Theoretical Computer Science - Words, languages and combinatorics
Computation: finite and infinite machines
Computation: finite and infinite machines
P Systems with Activated/Prohibited Membrane Channels
WMC-CdeA '02 Revised Papers from the International Workshop on Membrane Computing
Membrane Systems with Symport/Antiport Rules: Universality Results
WMC-CdeA '02 Revised Papers from the International Workshop on Membrane Computing
P Systems without Priorities Are Computationally Universal
WMC-CdeA '02 Revised Papers from the International Workshop on Membrane Computing
Results on catalytic and evolution-communication P systems
New Generation Computing - Membrane computing
Computationally universal P systems without priorities: two catalysts are sufficient
Theoretical Computer Science - Descriptional complexity of formal systems
Three "quantum" algorithms to solve 3-SAT
Theoretical Computer Science
(Tissue) P Systems with Unit Rules and Energy Assigned to Membranes
Fundamenta Informaticae - SPECIAL ISSUE MCU2004
Refining the nonterminal complexity of graph-controlled, programmed, and matrix grammars
Journal of Automata, Languages and Combinatorics
(UREM) P systems with a quantum-like behavior: background, definition, and computational power
WMC'07 Proceedings of the 8th international conference on Membrane computing
P systems with active membranes: trading time for space
Natural Computing: an international journal
Extended spiking neural p systems
WMC'06 Proceedings of the 7th international conference on Membrane Computing
Symbol/Membrane complexity of p systems with symport/antiport rules
WMC'05 Proceedings of the 6th international conference on Membrane Computing
Quantum sequential p systems with unit rules and energy assigned to membranes
WMC'05 Proceedings of the 6th international conference on Membrane Computing
On the efficiency of p systems with active membranes and two polarizations
WMC'04 Proceedings of the 5th international conference on Membrane Computing
WMC'04 Proceedings of the 5th international conference on Membrane Computing
Computational completeness of p systems with active membranes and two polarizations
MCU'04 Proceedings of the 4th international conference on Machines, Computations, and Universality
Sequential p systems with unit rules and energy assigned to membranes
MCU'04 Proceedings of the 4th international conference on Machines, Computations, and Universality
Register complexity of LOOP-, WHILE-, and GOTO-Programs
MCU'04 Proceedings of the 4th international conference on Machines, Computations, and Universality
Implementation of catalytic p systems
CIAA'04 Proceedings of the 9th international conference on Implementation and Application of Automata
(Tissue) P Systems with Unit Rules and Energy Assigned to Membranes
Fundamenta Informaticae - SPECIAL ISSUE MCU2004
Hi-index | 5.23 |
In addressing certain problems about membrane computing, a recent and active branch of natural computing, it first was necessary to address certain problems from the area of regulated rewriting. Thus, the present paper is a contribution to both these domains.A central problem in membrane computing is that of the hierarchy with respect to the number of membranes: Are systems with n + 1 membranes more powerful than systems with n membranes? Does the number of membranes induce an infinite hierarchy of the computed functions? Usually, when proving the universality of membrane systems (also called P systems), one starts from a matrix grammar and the number of membranes depends on the number of non-terminal symbols used by this grammar in the so-called appearance checking mode. We first prove that recursively enumerable languages can be generated by matrix grammars with only two non-terminal symbols being used in the appearance checking mode. The proofs of this fact and of several related results are based on a simulation of register machines by means of graph-controlled grammars.Then, we consider three classes of membrane systems, and in all the three cases the hierarchies with respect to the number of membranes are shown to collapse at level four: systems with four membranes are computationally universal (but we do not know whether or not this result is optimal).