We continue here the investigation of P automata, in their non-extended case, a class of
devices which characterize non-universal family of languages. First, a recent conjecture is
confirmed: any recursively enumerable language is obtained from a language recognized
by a P automaton, to which an initial (arbitrarily large) string is added. Then, we discuss
possibilities of extending P automata, following suggestions from string finite automata.
For instance, automata with a memory (corresponding to push-down automata) are
considered and their power is briefly investigated, as well as some closure properties of
the family of languages recognized by P automata. In the context, a brief survey of results
about P and dP automata (a distributed version of P automata) is provided, and several
further research topics are formulated.Junta de Andalucía P08-TIC-0420