@article {, title = {Rewriting P Systems with Conditional Communication }, journal = {Lecture Notes in Computer Science}, volume = {2300}, year = {2002}, pages = {325-353}, publisher = {Springer}, address = {Amsterdam, The Netherlands}, abstract = {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. }, issn = {0302-9743}, url = {http://www.springerlink.com/index/B69VXGXMY73WD34R.pdf}, author = {Paolo Bottoni and Anna Labella and Carlos Mart{\'\i}n-Vide and Gheorghe Paun} }