%0 Generic %D 2002 %T Rewriting P Systems with Conditional Communication %A Paolo Bottoni %A Anna Labella %A Carlos Martín-Vide %A Gheorghe Paun %C Amsterdam, The Netherlands %I Springer %P 325-353 %U http://www.springerlink.com/index/B69VXGXMY73WD34R.pdf %V 2300 %X A membrane system (P system) is a model of computation inspired by some basic features of the structure and behaviour of living cells. In this paper we consider systems with string-objects processed by rewriting, with the communication controlled by conditions on the contents of the strings. Symbols, substrings (in an arbitrary place, or as a prefix/suffix), or the shape of the whole string are used as permitting and as forbidding conditions when moving strings from a membrane to a neighboring membrane. Many of the obtained variants lead to new characterizations of recursively enumerable languages (as expected, these characterizations indicate a trade-off between the number of membranes and the strength of the communication conditions used). Several open problems are also formulated.