Resumo

ARANDA B., Jesús A.. On decidability properties of two fragments of the asynchronous π-calculus. Ing. compet. [online]. 2013, vol.15, n.2, pp.137-149. ISSN 0123-3033.

In (Cacciagrano, et al., 2008) the authors studied the expressiveness of persistence in the asynchronous p-calculus, henceforth Ap. They considered Ap and three sub-languages of it, each capturing one source of persistence: the persistent-input calculus (PIAp), the persistent-output calculus (POAp), and the persistent calculus (PAp). They prove that, under some general conditions, there cannot be an encoding from Ap into a (semi)-persistent calculus preserving the must-testing semantics, a semantics sensitive to divergence. In this paper we support and strengthen the separation results of (Cacciagrano, et al., 2008) by showing that convergence and divergence are two decidable properties in a fragment of POAp and PAp, in contrast to what happen in Ap. Thus, it is shown that there cannot be a (computable) encoding from Ap into PAp and in such a fragment of POAp, preserving divergence or convergence. These impossibility results don't presuppose any condition on the encodings and involve directly convergence for first time in the study of the expressiveness of persistence of Aπ

Palavras-chave : Expressiveness; divergence; convergence; process calculi.

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