We introduce explicit fusions of names. An explicit fusion is a process that exists concurrently with the rest of the system and enables two names to be used interchangeably. Explicit fusions provide a small-step account of reaction in process calculi such as the pi calculus and the fusion calculus. In this respect they are similar to the explicit substitutions of Abadi, Cardelli and Curien, which do the same for the lambda calculus. In this paper, we give a technical foundation for explicit fusions. We present the pi-F calculus, a simple process calculus with explicit fusions, and define a strong bisimulation congruence. We study the embeddings of the fusion calculus and the pi calculus. The former is fully abstract with respect to bisimulation.

Abstract. We describe a methodology for assembling composite services based on three basic processes which are independent of the concrete implementation: Service Abstraction Process, Service Composition Process, and Translation Process. These processes share the concept of integrated component composed of two key aspects: a specific set of the Aalst’s workflow patterns together with a component-style composition of complex services. We propose a novel approach that implements the steps of such methodology, providing an efficient manner for developing service compositions and enhancing the expressiveness of target composition languages like BPEL4WS. Here we focus on the description of the Service Abstraction Process, a critical step in order to enhance the service composition by facilitating the reuse of existing services. 1

The article discusses causal models, such as Petri nets and event structures, how they have been rediscovered in a wide variety of recent applications, and why they are fundamental to computer science. A discussion of their present limitations leads to their extension with symmetry. The consequences, actual and potential, are discussed.

Abstract. The finite π-calculus has an explicit set-theoretic functor-category model that is known to be fully abstract for strong late bisimulation congruence. We characterize this as the initial free algebra for an appropriate set of operations and equations in the enriched Lawvere theories of Plotkin and Power. Thus we obtain a novel algebraic description for models of the π-calculus, and validate an existing construction as the universal such model. The algebraic operations are intuitive, covering name creation, communication of names over channels, and nondeterminism; the equations then combine these features in a modular fashion. We work in an enriched setting, over a “possible worlds ” category of sets indexed by available names. This expands significantly on the classical notion of algebraic theories, and in particular allows us to use nonstandard arities that vary as processes evolve. Based on our algebraic theory we describe a category of models for the π-calculus, and show that they all preserve bisimulation congruence. We develop a direct construction of free models in this category; and generalise previous results to prove that all free-algebra models are fully abstract. 1