P Systems Generating Trees.

We consider P systems with active membranes, but without polarizations, yet with using membrane division and membrane generation, but as the result of a halting computation we do not take the terminal string generated in a designated output membrane, instead we consider the resulting tree representing the membrane structure of the final configuration as its result. We show that each recursively enumerable tree language can be obtained in that way generated by P systems with active membranes working on strings. [ABSTRACT FROM AUTHOR]