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A Presheaf Semantics of ValuePassing Processes
, 1996
"... This paper investigates presheaf models for process calculi with value passing. Denotational semantics in presheaf models are shown to correspond to operational semantics in that bisimulation obtained from open maps is proved to coincide with bisimulation as defined traditionally from the operat ..."
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Cited by 33 (18 self)
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This paper investigates presheaf models for process calculi with value passing. Denotational semantics in presheaf models are shown to correspond to operational semantics in that bisimulation obtained from open maps is proved to coincide with bisimulation as defined traditionally from the operational semantics. Both "early" and "late" semantics are considered, though the more interesting "late" semantics is emphasised. A presheaf model and denotational semantics is proposed for a language allowing process passing, though there remains the problem of relating the notion of bisimulation obtained from open maps to a more traditional definition from the operational semantics.
History Dependent Automata
, 2001
"... In this paper we present historydependent automata (HDautomata in brief). They are an extension of ordinary automata that overcomes their limitations in dealing with historydependent formalisms. In a historydependent formalism the actions that a system can perform carry information generated i ..."
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Cited by 28 (8 self)
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In this paper we present historydependent automata (HDautomata in brief). They are an extension of ordinary automata that overcomes their limitations in dealing with historydependent formalisms. In a historydependent formalism the actions that a system can perform carry information generated in the past history of the system. The most interesting example is calculus: channel names can be created by some actions and they can then be referenced by successive actions. Other examples are CCS with localities and the historypreserving semantics of Petri nets. Ordinary
Mathematical models of computational and combinatorial structures. Invited address for Foundations
 of Software Science and Computation Structures (FOSSACS 2005
, 2005
"... Abstract. The general aim of this talk is to advocate a combinatorial perspective, together with its methods, in the investigation and study of models of computation structures. This, of course, should be taken in conjunction with the wellestablished views and methods stemming from algebra, category ..."
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Cited by 9 (3 self)
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Abstract. The general aim of this talk is to advocate a combinatorial perspective, together with its methods, in the investigation and study of models of computation structures. This, of course, should be taken in conjunction with the wellestablished views and methods stemming from algebra, category theory, domain theory, logic, type theory, etc. In support of this proposal I will show how such an approach leads to interesting connections between various areas of computer science and mathematics; concentrating on one such example in some detail. Specifically, I will consider the line of my research involving denotational models of the pi calculus and algebraic theories with variablebinding operators, indicating how the abstract mathematical structure underlying these models fits with that of Joyal’s combinatorial species of structures. This analysis suggests both the unification and generalisation of models, and in the latter vein I will introduce generalised species of structures and their calculus. These generalised species encompass and generalise various of the notions of species used in combinatorics. Furthermore, they have a rich mathematical structure (akin to models of Girard’s linear logic) that can be described purely within Lawvere’s generalised logic. Indeed, I will present and treat the cartesian closed structure, the linear structure, the differential structure, etc. of generalised species axiomatically in this mathematical framework. As an upshot, I will observe that the setting allows for interpretations of computational calculi (like the lambda calculus, both typed and untyped; the recently introduced differential lambda calculus of Ehrhard and Regnier; etc.) that can be directly seen as translations into a more basic elementary calculus of interacting agents that compute by communicating and operating upon structured data.
Formal Development of Open Distributed Systems: towards an Integrated Framework
 In Proceedings of Workshop on ObjectOriented Specification Techniques for Distributed Systems and Behaviours (OOSDS’99
, 1999
"... . This paper contributes to the discussion on the issues related to the formal development of open distributed systems. The deficiencies of traditional formal notations in this setting are highlighted. We argue that there is no single formalism exhibiting all the features required. As a solution ..."
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Cited by 6 (3 self)
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. This paper contributes to the discussion on the issues related to the formal development of open distributed systems. The deficiencies of traditional formal notations in this setting are highlighted. We argue that there is no single formalism exhibiting all the features required. As a solution, we propose a multiformalism platform that involves three formalisms: UML, OUN and PVSSL. We discuss the motivation for the choice of these formalisms and the main research issues underlying this kind of platform. Keywords: Formal Methods, Open Distributed Systems, UML, PVS, OUN, Multiformalism, Objectorientation. 1 Introduction and Problem Statement Motivated by the need for modeling the dynamic features of objectoriented programming languages and openness in distributed applications, the study of open, dynamically extendable systems has become a very popular research area. In fact, since the late 80ies, much research within theoretical computer science has been directed towards t...
Structured Coalbegras and Minimal HDAutomata for the πCalculus
, 2000
"... The coalgebraic framework developed for the classical process algebras, and in particular its advantages concerning minimal realizations, does not fully apply to the picalculus, due to the constraints on the freshly generated names that appear in the bisimulation. In this paper we propose to model ..."
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The coalgebraic framework developed for the classical process algebras, and in particular its advantages concerning minimal realizations, does not fully apply to the picalculus, due to the constraints on the freshly generated names that appear in the bisimulation. In this paper we propose to model the transition system of the πcalculus as a coalgebra on a category of name permutation algebras and to define its abstract semantics as the final coalgebra of such a category. We show that permutations are sufficient to represent in an explicit way fresh name generation, thus allowing for the definition of minimal realizations. We also link the coalgebraic semantics with a slightly improved version of history dependent (HD) automata, a model developed for verification purposes, where states have local names and transitions are decorated with names and name relations. HDautomata associated with agents with a bounded number of threads in their derivatives are finite and can be actually minimized. We show that the bisimulation relation in the coalgebraic context corresponds to the minimal HDautomaton.
MFPS 2011 A resource analysis of the πcalculus
"... We give a new treatment of the πcalculus based on the semantic theory of separation logic, continuing a research program begun by Hoare and O’Hearn. Using a novel resource model that distinguishes between public and private ownership, we refactor the operational semantics so that sending, receiving ..."
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We give a new treatment of the πcalculus based on the semantic theory of separation logic, continuing a research program begun by Hoare and O’Hearn. Using a novel resource model that distinguishes between public and private ownership, we refactor the operational semantics so that sending, receiving, and allocating are commands that influence owned resources. These ideas lead naturally to two denotational models: one for safety and one for liveness. Both models are fully abstract for the corresponding observables, but more importantly both are very simple. The close connections with the model theory of separation logic (in particular, with Brookes’s action trace model) give rise to a logic of processes and resources. Keywords: separation logic, picalculus, ownership, resources, scope extrusion, full abstraction Names play a leading role in the πcalculus [12]: they are both the means of communication, and the data communicated. This paper presents a study of the πcalculus based on a new mechanism for name management, which is in turn rooted in separation logic. The main benefit of this study is a very simple—but fully abstract—denotational semantics for the πcalculus. Traditionally, the use of names in the πcalculus is governed by lexical, but dynamicallyexpandable, scope. In the composite process P ∣new x.Q for example, the channel x is by virtue of scope initially private to Q. The prefix new x is not an imperative allocation. It is a binder that remains fixed as Q evolves—a constant reminder that x is private—until Q sends x in a message. At that point, the binder is lifted to cover both P and Q, dynamically “extruding ” the scope of x. The πcalculus relies on αrenaming and side conditions about freshness to ensure that its privacy narrative is borne out. In contrast, work on separation logic has led to models of dynamicallystructured concurrency based on resources and ownership, rather than names This paper is electronically published in