Formal languages
Theory of recursive functions and effective computability
Theory of recursive functions and effective computability
Petri net algorithms in the theory of matrix grammars
Acta Informatica
A Machine-Independent Theory of the Complexity of Recursive Functions
Journal of the ACM (JACM)
Theory of Computation
Membrane Computing: An Introduction
Membrane Computing: An Introduction
The power of communication: P systems with symport/antiport
New Generation Computing
Membrane Systems with Symport/Antiport Rules: Universality Results
WMC-CdeA '02 Revised Papers from the International Workshop on Membrane Computing
Computationally universal P systems without priorities: two catalysts are sufficient
Theoretical Computer Science - Descriptional complexity of formal systems
Computation: finite and infinite machines
Computation: finite and infinite machines
Symport/Antiport P Systems with Three Objects Are Universal
Fundamenta Informaticae - Contagious Creativity - In Honor of the 80th Birthday of Professor Solomon Marcus
Fundamenta Informaticae
Proceedings of the 5th international conference on Membrane Computing
WMC'04 Proceedings of the 5th international conference on Membrane Computing
Communicative p systems with minimal cooperation
WMC'04 Proceedings of the 5th international conference on Membrane Computing
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We briefly investigate the idea to consider as the result of a computation in a P system the number of steps elapsed between two events produced during the computation. Specifically, we first consider the case when the result of a computation is defined in terms of events related to using rules, introducing objects, or meeting objects. In each case, symport/antiport P systems are computationally complete, i.e., they can generate any recursively enumerable set of natural numbers. Then, we address the case when the number computed by a system is the length of a computation itself. We obtain a few results both for catalytic multiset-rewriting and for symport/antiport systems (in each case, also with using membrane dissolution) showing that non-semilinear sets of vectors of natural numbers can be computed in that way. Moreover, we prove a general result showing that for no type of systems we can obtain computational completeness when considering the length sets of halting computations. The general problem, of characterizing the sets of natural numbers computed in this way, remains open.