Symmetries, local names and dynamic (de)-allocation of names

The semantics of name-passing calculi is often defined employing coalgebraic models over presheaf categories This elegant theory lacks finiteness properties hence it is not apt to implementation Coalgebras over named sets, called history-dependent automata are better suited for the purpose due to locality of names A theory of behavioural functors for named sets is still lacking the semantics of each language has been given in an ad-hoc way and algorithms were implemented only for the pi-calculus Existence of the final coalgebra for the pi-calculus was never proved We introduce a language of accessible functors to specify history-dependent automata in a modular way leading to a clean formulation and a generalisation of previous results and to the proof of existence of a final coalgebra in a wide range of cases (C) 2010 Elsevier Inc All rights reserve