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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 π-calculus. Existence of the final coalgebra for the π-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.

The problem of defining fully abstract operational models of name passing calculi has been given some elegant solutions, such as coalgebras over presheaf categories or over nominal sets. These formalisms fail to model garbage collection of unused names, hence they do not have nice properties with respects to finite state algorithms. The category of named sets, on the other hand, was designed for the purpose of supporting efficient algorithms to handle the semantics of name passing calculi. However the theory was developed in a rather ad-hoc fashion (e.g. the existence of a final coalgebra was only proved in the finite case). In this work we introduce a name abstraction functor for named sets and show that it provides a simple and effective notion of garbage collection of unused names. Along the way, we survey a number of needed results on the category of permutation algebras, an algebra-theoretic definition of nominal sets. In particular we give a formalization of the adjunction between abstraction and concretion, an example illustrating a nominal syntax alike handling of De Bruijn indexes, and an explicit functor to model the early semantics of the π-calculus in nominal sets.

The Signal Calculus is an asynchronous process calculus featuring multicast communication. It relies on explicit modeling of the communication structure of the network (communication flows), and on handling sessions, even multi-party. The calculus is strongly motivated by the practical needs of Service-Oriented Computing, and there exists a Java implementation, called JSCL, with a graphical modeling framework. To the aim of adding to SC (and JSCL) a verification environment, in this work we introduce the abstract semantics of SC, based on bisimulation. We show an example exploiting bisimilarity to prove the correctness of an SC model with respects to a transactional isolation requirement.

An important issue of the service oriented approach is the possibility to aggregate, through programmable coordination patterns, the activities involved by service interactions. Two different approaches can be adopted to tackle service coordination: orchestration and choreography. In this paper, we introduce a formal methodology purposed to handle coordination among services from the perspective of a global observer, in the spirit of choreography models. In particular, we address the problem of verifying compliance and consistency between the design of service interactions and the choreography constraints.

Name passing calculi are nowadays an established field on its own. Besides their practical relevance, they offered an intriguing challenge, since the standard operational, denotational and logical methods often proved inadequate to reason about these formalisms. A domain which has been successfully employed for languages with asymmetric communication, like the π-calculus, are presheaf categories based on (injective) relabelings, such as Set^I. Calculi with symmetric binding, in the spirit of the fusion calculus, pose new challenges. In this work, we examine the calculus of explicit fusions, and propose to model its syntax and semantics using the presheaf category Set^E, where E is the category of equivalence relations and equivalence preserving morphisms.

We use History Dependent Automata as a syntax-indepentend formalism to check compatibility of services at binding time in Service-Oriented Computing. Informally speaking, service requests are modelled as pairs of HD-automata < C_o,C_r >; C_r describes the (abstract) behaviour of the searched service and C_o the (abstract) behaviour guaranteed by the invoker. Symmetrically, service publication consists of a pair of HD-automata < S_o,S_r > such that S_o provides an (abstraction of) of the behaviour guaranteed by the service and S_r yields the requirement imposed to invokers. An invocation < C_o,C_r > matches a published interface < S_o,S_r > when C_o simulates S_r and S_o simulates C_r.

We introduce a class of coalgebraic models and a family of modal logics that support the specification of spatial properties of distributed applications. The evaluation of a formula yields a value in a suitable multi-valued algebraic structure, giving a measure of the satisfaction of a requirement, induced by the decomposition of a system into subsystems, meant as available resources. As semantic domain we consider certain algebraic structures, called c-semirings, that allow us to generalize boolean logics to the multi-valued case, while keeping a number of the axioms of boolean algebras. Under suitable conditions on the structure of c-semirings, we show that, even if our logical formalisms are equipped with spatial operators, the interpretation of formulas fully characterizes bisimilarity.