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The Fusion Calculus: Expressiveness and Symmetry in Mobile Processes (Extended Abstract)
 LICS'98
, 1998
"... We present the fusion calculus as a significant step towards a canonical calculus of concurrency. It simplifies and extends the πcalculus.
The fusion calculus contains the polyadic πcalculus as a proper subcalculus and thus inherits all its expressive power. The gain is that fusion contains action ..."
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Cited by 138 (14 self)
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We present the fusion calculus as a significant step towards a canonical calculus of concurrency. It simplifies and extends the πcalculus.
The fusion calculus contains the polyadic πcalculus as a proper subcalculus and thus inherits all its expressive power. The gain is that fusion contains actions akin to updating a shared state, and a scoping construct for bounding their effects. Therefore it is easier to represent computational models such as concurrent constraints formalisms. It is also easy to represent the so called strong reduction strategies in the lambdacalculus, involving reduction under abstraction. In the πcalculus these tasks require elaborate encodings.
The dramatic main point of this paper is that we achieve these improvements by simplifying the πcalculus rather than adding features to it. The fusion calculus has only one binding operator where the πcalculus has two (input and restriction). It has a complete symmetry between input and output actions where the πcalculus has not. There is only one sensible variety of bisimulation congruence where the picalculus has at least three (early, late and open). Proofs about the fusion calculus, for example in complete axiomatizations and full abstraction, therefore are shorter and clearer.
Our results on the fusion calculus in this paper are the following. We give a structured operational semantics in the traditional style. The novelty lies in a new kind of action, fusion actions for emulating updates of a shared state. We prove that the calculus contains the πcalculus as a subcalculus. We define and motivate the bisimulation equivalence and prove a simple characterization of its induced congruence, which is given two versions of a complete axiomatization for finite terms. The expressive power of the calculus is demonstrated by giving a straightforward encoding of the strong lazy lambdacalculus, which admits reduction under lambda abstraction.
The Update Calculus
, 1997
"... In the update calculus concurrent processes can perform update actions with side effects, and a scoping operator can be used to control the extent of the update. In this way it incorporates fundamental concepts both from imperative languages or concurrent constraints formalisms, and from functional ..."
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Cited by 83 (3 self)
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In the update calculus concurrent processes can perform update actions with side effects, and a scoping operator can be used to control the extent of the update. In this way it incorporates fundamental concepts both from imperative languages or concurrent constraints formalisms, and from functional formalisms such as the  and calculi. Structurally it is similar to but simpler than the calculus; it has only one binding operator and a symmetry between input and output. We define the structured operational semantics and the proper bisimulation equivalence and congruence, and give a complete axiomatization. The calculus turns out to be an asymmetric subcalculus. 1 Introduction Theory of concurrent computation is a diverse field where many different approaches have been proposed and no consensus has emerged on the best paradigms. In this paper we take a step towards unifying two seemingly contradictory schools of thought: global vs local effects of concurrent actions. We define a calc...
Testing equivalence for mobile processes
 Proceedings of CONCUR ’92, LNCS 630
, 1995
"... Abst rac t. The impact of applying the testing approach to a calculus of processes with a dynamically changing structure is investigated. A proof system for the finite fragment of the calculus is introduced which consists of two groups of laws: those for strong observational equivalence and those ne ..."
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Cited by 71 (10 self)
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Abst rac t. The impact of applying the testing approach to a calculus of processes with a dynamically changing structure is investigated. A proof system for the finite fragment of the calculus is introduced which consists of two groups of laws: those for strong observational equivalence and those needed to deal with x actions. Soundness and completeness w.r.t, a testing preorder are shown. A fully abstract denotational model for the language is presented which relies on the existence of normal forms for processes. 1.
A Theory of Bisimulation for the picalculus
, 1993
"... We study a new formulation of bisimulation for the calculus [MPW92], which we have called open bisimulation ( ). In contrast with the previously known bisimilarity equivalences, is preserved by all calculus operators, including input prefix. The differences among all these equivalences alread ..."
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Cited by 66 (0 self)
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We study a new formulation of bisimulation for the calculus [MPW92], which we have called open bisimulation ( ). In contrast with the previously known bisimilarity equivalences, is preserved by all calculus operators, including input prefix. The differences among all these equivalences already appear in the sublanguage without name restrictions: Here the definition of can be factorised into a "standard" part which, modulo the different syntax of actions, is the CCS bisimulation, and a part specific to the calculus, which requires name instantiation. Attractive features of are: a simple axiomatisation (of the finite terms), with a completeness proof which leads to the construction of minimal canonical representatives for the equivalence classes of ; an "efficient" characterisation, based on a modified transition system. This characterisation seems promising for the development of automatedverification tools and also shows the callbyneed flavour of . Although in the...
Bisimulation for higherorder process calculi
 INFORMATION AND COMPUTATION
, 1996
"... A higherorder process calculus is a calculus for communicating systems which contains higherorder constructs like communication of terms. We analyse the notion of bisimulation in these calculi. We argue that both the standard definition of bisimulation (i.e., the one for CCS and related calculi), ..."
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Cited by 64 (5 self)
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A higherorder process calculus is a calculus for communicating systems which contains higherorder constructs like communication of terms. We analyse the notion of bisimulation in these calculi. We argue that both the standard definition of bisimulation (i.e., the one for CCS and related calculi), as well as higherorder bisimulation [E. Astesiano,
On the expressiveness of internal mobility in namepassing calculi
, 1998
"... We consider the language rI, a namepassing calculus introduced by Sangiorgi, where only private names can be exchanged among processes (internal mobility). The calculus 7cI has simple mathematical theory, very close to that of CCS. We provide an encoding from (an asynchronous variant of) the ~rca ..."
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Cited by 41 (0 self)
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We consider the language rI, a namepassing calculus introduced by Sangiorgi, where only private names can be exchanged among processes (internal mobility). The calculus 7cI has simple mathematical theory, very close to that of CCS. We provide an encoding from (an asynchronous variant of) the ~rcalculus to IrI, which is fully abstract on the reduction relations of the two calculi. The result shows that, in namepassing calculi, internal mobility is the essential ingredient as far as expressiveness i concerned. 1 In t roduct ion By now, the 7rcalculus [13] is generally recognized as the prototypical algebraic language for describing concurrent systems with dynamically evolving communication linkage. The latter phenomenon, known as mobility, is modelled through the passing of channel names among processes (namepassing). The expressive power of the ~rcalculus is demonstrated by the existence of simple and fully abstract ranslations into it for a variety of computational formalisms, including Acalculus [12], higherorder process calculi [15] and calculi which permits reasoning on the causal or spatial structure of the systems [4, 17]. The price to pay for this expressiveness i a rather complex mathematical theory of the rcalculus. A source of complications i, above all, the need to take name instantiation (otherwise called substitution) into account. Input and output at a of a tuple of names b are written, respectively, asa(b).P (input prefix) and ~(b).P (output prefix), with P representing the continuation of the prefix. An input and an output prefix can be consumed in a communication, where a tuple of names is passed and used to instantiate the formal parameters of the input prefix, thus: a(c).P]5<b>.Q ~, P{b/~}]Q (,) with {b~} denoting the instantiation ofnames in ~'with names in b. Name instantiation is a central aspect in the mathematical treatment of certain behavioural relations.
Contracts for mobile processes
 In CONCUR 2009, number 5710 in LNCS
, 2009
"... Abstract. Theories identifying wellformed systems of processes—those that lack communication errors and enjoy strong properties such as deadlock freedom— are based either on session types, which are inhabited by channels, or on contracts, which are inhabited by processes. Current session type theor ..."
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Cited by 24 (4 self)
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Abstract. Theories identifying wellformed systems of processes—those that lack communication errors and enjoy strong properties such as deadlock freedom— are based either on session types, which are inhabited by channels, or on contracts, which are inhabited by processes. Current session type theories impose overly restrictive disciplines while contract theories only work for networks with fixed topology. Here we fill the gap between the two approaches by defining a theory of contracts for socalled mobile processes, those whose communications may include delegations and channel references. 1
A Broadcastbased Calculus for Communicating Systems
, 2000
"... This paper presents a process calculus for recongurable communicating systems which has broadcast as basic communication primitive, and we provide an operational semantics for this calculus. We illustrate the calculus through some examples, and we propose three behavioral equivalences for reasoning ..."
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Cited by 19 (1 self)
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This paper presents a process calculus for recongurable communicating systems which has broadcast as basic communication primitive, and we provide an operational semantics for this calculus. We illustrate the calculus through some examples, and we propose three behavioral equivalences for reasoning about systems of broadcasting processes, namely, barbed equivalence, stepequivalence and labelled bisimilarity. An important result, is that all these relations coincide, providing dierent ways to study the equivalence/nonequivalence of two systems. Then, we provide a direct characterization for the strong congruence relation induced by these equivalences. Finally, we give a complete axiomatisation for strong congruence. 1
Minimality and Separation Results on Asynchronous Mobile Processes  Representability Theorems by Concurrent Combinators (Extended Abstract)
 In Proceedings of CONCUR '98, number 1466 in Lecture Notes in Computer Science
, 1998
"... ) y Nobuko Yoshida ? Abstract. In [18, 19], we presented a theory of concurrent combinators for the asynchronous monadic ßcalculus without match or summation operator [7, 16]. The system of concurrent combinators is based on a finite number of atoms and fixed interaction rules, but is as expressi ..."
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Cited by 15 (1 self)
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) y Nobuko Yoshida ? Abstract. In [18, 19], we presented a theory of concurrent combinators for the asynchronous monadic ßcalculus without match or summation operator [7, 16]. The system of concurrent combinators is based on a finite number of atoms and fixed interaction rules, but is as expressive as the original calculus, so that it can represent diverse interaction structures, including polyadic synchronous name passing [23] and input guarded summations [26]. The present paper shows that each of the five basic combinators introduced in [18] is indispensable to represent the whole computation, i.e. if one of the combinators is missing, we can no longer express the original calculus up to weak bisimilarity. Expressive power of several interesting subsystems of the asynchronous ßcalculus is also measured by using appropriate subsets of the combinators and their variants. Finally as an application of the main result, we show there is no semantically sound encoding of the calculus in...
A symbolic semantics for the picalculus
 Inf. and Comp
, 1996
"... We use symbolic transition systems as a basis for providing the picalculus with an alternative semantics. The latter is more amenable to automatic manipulation and sheds light on the logical differences among different forms of bisimulation over algebras of namepassing processes. Symbolic transiti ..."
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Cited by 15 (1 self)
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We use symbolic transition systems as a basis for providing the picalculus with an alternative semantics. The latter is more amenable to automatic manipulation and sheds light on the logical differences among different forms of bisimulation over algebras of namepassing processes. Symbolic transitions have the form P φ, α7− → P ′, where φ is a boolean combination of equalities on names that has to hold for the transition to take place, and α is standard a picalculus action. On top of the symbolic transition system, a symbolic bisimulation is defined that captures the standard ones. Finally, a sound and complete proof system is introduced for symbolic bisimulation. 1