Abstract
The aim of this paper is to show how the P systems with replicated rewriting can be modeled by X-machines (also called Eilenberg machines). In the first approach, the parallel behaviour of the regions of a P system is simulated by a sequential process involving a single X-machine. This allows the application of the X-machine testing procedures in order to prove the correctness of P systems. In the second approach, a P system is simulated by a communicating system of X-machines. Each component of such a system is an X-machine associated with a region of the given P system. The components act in parallel, as their counterparts do in a P system, and use some specific mechanism for communication and synchronisation.