This paper aims to answer the following question: given a P system configuration  M  , how do we find each configuration  N  such that  N  evolves to  M  in one step? While easy to state, the problem has not a simple answer. To provide a solution to this problem for a general class of P systems with simple communication rules and without dissolution, we introduce the dual P systems. Essentially these systems reverse the rules of the initial P system and find  N  by applying reversely valid multisets of rules. We prove that in this way we find exactly those configurations  N  which evolve to  M  in one step.
['Oana Agrigoroaiei', 'Gabriel Ciobanu']
Dual P Systems