Vendredi 12 Juillet

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Vendredi 12 Juillet
Heure: 00:59 - 12:00
Lieu: Amphi Copernic, Institut Galilée, Université de Villetaneuse
Résumé: Bisimulations from graphical encodings (DPOs, RPOs, cospans, and all that)
Description: Fabio Gadducci The talk presents a personal recollection of recent results on the synthesis of labelled transition systems (LTSs) for process calculi.
The starting point is a visual technique for modelling the reduction semantics of nominal calculi: processes are mapped into graphs equipped with "interfaces", such that the denotation is fully abstract with respect to the structural congruence. The encoding allows for the reuse of standard graph rewriting theory and tools for simulating the reduction semantics of the calculus, such as the "double pushout" (DPO) approach and its concurrent semantics (which allows for the simultaneous execution of independent reductions)
Graphs with interfaces are just an instance of a cospan category (over the category of graphs). which is amenable to the synthesis mechanism based on "borrowed contexts" (BCs), proposed by Ehrig and Koenig, which are in turn an instance of "relative push outs" (RPOs), originally introduced by Milner and Leifer. The BC mechanism allows for the effective construction of an LTS that has graphs with interfaces as both states and labels, and such that the associated bisimilarity is automatically a congruence.
Since the category of cospans over graphs admits RPOs (as proved by Sassone and Sobocinski), its choice as the domain of the encoding for nominal calculi ensures that the synthesis of an LTS can be performed, and that a compositional observational equivalence is obtained. The talk discusses the LTS distilled by exploiting the encoding of CCS and Mobile Ambients processes.