P Systems with Tables of Rules

Abstract

In the last time, several e®orts were made in order to remove the polarization of membranes from P systems with active membranes; the present paper is a contribution in this respect. In order to compensate the loss of power represented by avoiding polarizations, we introduce tables of rules: each membrane has associated several sets of rules, one of which is non- deterministically chosen in each computation step. Three universality results for tabled P systems are given, trying to use rules of as few as possible types. Then, we consider tables with obligatory rules { rules which must be applied at least once when the table is applied. Systems which use tables with at most one obligatory rule are proven to be able to solve SAT problem in linear time. Several open problems are also formulated.