The paper gives several results regarding P systems with non-cooperative rules and promoters/inhibitors at the level of rules. For the class of P systems using inhibitors, generating families of sets of vectors of numbers, the equivalence with the family of Parikh sets of ET0L languages is presented. In case of P systems with noncooperative promoted rules even if an upper bound was not given, the inclusion of the family P sET 0L was proved. Moreover, a characterization of such systems by means

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... f a particular form of random context grammars, therefore a sequential formal device, is proposed.