Minimisation of event structures

Event structures are fundamental models in concurrency theory, providing a representation of events in computation and of their relations, notably concurrency, conflict and causality. In this paper we present a theory of minimisation for event structures. Working in a class of event structures that generalises many stable event structure models in the literature, (e.g., prime, asymmetric, flow and bundle event structures) we study a notion of behaviour-preserving quotient, taking hereditary history preserving bisimilarity as a reference behavioural equivalence. We show that for any event structure a uniquely determined minimal quotient always exists. We observe that each event structure can be seen as the quotient of a prime event structure, and that quotients of general event structures arise from quotients of (suitably defined) corresponding prime event structures. This gives a special relevance to quotients in the class of prime event structures, which are then studied in detail, providing a characterisation and showing that also prime event structures always admit a unique minimal quotient

Bisimulations respecting duration and causality for the non-interleaving applied pi-calculus

This paper shows how we can make use of an asynchronous transition system, whose transitions are labelled with events and which is equipped with a notion of independence of events, to define non-interleaving semantics for the applied π-calculus. The most important notions we define are: Start-Termination or ST-bisimilarity, preserving duration of events; and History-Preserving or HP- bisimilarity, preserving causality. We point out that corresponding similarity preorders expose clearly distinctions between these semantics. We draw particular attention to the distinguishing power of HP failure similarity, and discuss how it affects the attacker threat model against which we verify security and privacy properties. We also compare existing notions of located bisimilarity to the definitions we introduce

Reversibility in the higher-order π-calculus

The notion of reversible computation is attracting increasing interest because of its applications in diverse fields, in particular the study of programming abstractions for reliable systems. In this paper, we continue the study un-dertaken by Danos and Krivine on reversible CCS by defining a reversible higher-order π-calculus, called rhoπ. We prove that reversibility in our cal-culus is causally consistent and that the causal information used to support reversibility in rhoπ is consistent with the one used in the causal semantics of the π-calculus developed by Boreale and Sangiorgi. Finally, we show that one can faithfully encode rhoπ into a variant of higher-order π, substantially improving on the result we obtained in the conference version of this paper

Typed Event Structures and the linear pi-calculus

International audienceWe propose a typing system for the true concurrent model of event structures that guarantees the interesting behavioural properties known as conflict freeness and confusion freeness. Conflict freeness is the true concurrent version of the notion of confluence. A system is confusion free if nondeterministic choices are localised and do not depend on the scheduling of independent components. Ours is the first typing system to control behaviour in a true concurrent model. To demonstrate its applicability, we show that typed event structures give a semantics of linearly typed version of the π-calculi with internal mobility. The semantics we provide is the first event structure semantics of the π-calculus and generalises Winskel's original event structure semantics of CCS