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13
On Asynchrony in NamePassing Calculi
 In
, 1998
"... The asynchronous picalculus is considered the basis of experimental programming languages (or proposal of programming languages) like Pict, Join, and Blue calculus. However, at a closer inspection, these languages are based on an even simpler calculus, called Local (L), where: (a) only the output c ..."
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The asynchronous picalculus is considered the basis of experimental programming languages (or proposal of programming languages) like Pict, Join, and Blue calculus. However, at a closer inspection, these languages are based on an even simpler calculus, called Local (L), where: (a) only the output capability of names may be transmitted; (b) there is no matching or similar constructs for testing equality between names. We study the basic operational and algebraic theory of Lpi. We focus on bisimulationbased behavioural equivalences, precisely on barbed congruence. We prove two coinductive characterisations of barbed congruence in Lpi, and some basic algebraic laws. We then show applications of this theory, including: the derivability of delayed input; the correctness of an optimisation of the encoding of callbyname lambdacalculus; the validity of some laws for Join.
A Process Algebraic View of Linda Coordination Primitives
, 1998
"... The main Linda coordination primitives (asynchronous communication, read operation, nonblocking in/rd predicates) are studied in a process algebraic setting. A lattice of eight languages is proposed, where its bottom element L is a process algebra differing from CCS only for the asynchrony of the ou ..."
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The main Linda coordination primitives (asynchronous communication, read operation, nonblocking in/rd predicates) are studied in a process algebraic setting. A lattice of eight languages is proposed, where its bottom element L is a process algebra differing from CCS only for the asynchrony of the output operation, while all the other languages in the lattice are obtained as extension of this basic language by adding some of the Linda coordination primitives. The observational semantics for these languages are all obtained as the coarsest congruences contained in the barbed semantics, where only tuples are observable. The lattice of the eight languages collapses to a smaller fourpoints lattice of different bisimulationbased semantics. Notably, for L this semantics is the standard notion of strong bisimulation, where inputs and outputs/tuples are treated symmetrically. Keywords: Coordination languages, Semantics of Linda, Process algebra. 1 Introduction The aim of this paper is to pr...
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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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.
Trace and Testing Equivalence on Asynchronous Processes
 Information and Computation
, 1999
"... We study trace and maytesting equivalences in the asynchronous versions of CCS and calculus. We start from the operational definition of the maytesting preorder and provide for it finitary and fully abstract tracebased characterizations, along with a complete inequational proof system. We also ..."
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Cited by 36 (5 self)
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We study trace and maytesting equivalences in the asynchronous versions of CCS and calculus. We start from the operational definition of the maytesting preorder and provide for it finitary and fully abstract tracebased characterizations, along with a complete inequational proof system. We also touch upon two variants of this theory, by first considering a more demanding equivalence notion (musttesting) and then a richer version of asynchronous CCS. The results throw light on the difference between synchronous and asynchronous communication and on the weaker testing power of asynchronous observations. Keywords: Asynchronous Communications, Process Algebras, Semantics. This paper is an extended and revised version of [8] and [9]. 1 Contents 1 Introduction 3 2 Asynchronous CCS 5 2.1 Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2 Operational semantics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.3 Maytesting semant...
Comparing Three Semantics for Lindalike Languages
 Theoretical Computer Science
"... A simple calculus based on generative communication is introduced; among its primitives, it contains a conditional input operation that tests for presence (or absence) of an output, reminiscent of the inp predicate of Linda. We study three different semantics for the output operation, called instant ..."
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A simple calculus based on generative communication is introduced; among its primitives, it contains a conditional input operation that tests for presence (or absence) of an output, reminiscent of the inp predicate of Linda. We study three different semantics for the output operation, called instantaneous, ordered and unordered, and we compare these approaches from two different points of view. First, we investigate the associated behavioural semantics by characterizing the coarsest congruence contained in the barbed bisimulation. We obtain the following results: in the instantaneous case the coarsest congruence is a variant of asynchronous bisimulation while, for the ordered and unordered semantics, we obtain a small variant of the classic (synchronous) bisimulation. Moreover, the three obtained congruences are pairwise different. Then, we compare the expressiveness of the three approaches. We first list a class of coordination primitives that are directly implementable in our calcul...
Three Semantics of the Output Operation for Generative Communication
 In Coordination Languages and Models, Proceedings of the second international conference COORDINATION'97
, 1997
"... . A simple, yet Turing powerful, calculus based on generative communication is introduced; among its primitives, it contains a conditional input operation that tests for presence (or absence) of an output, reminiscent of the inp predicate of Linda. We study three different operational semantics for ..."
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. A simple, yet Turing powerful, calculus based on generative communication is introduced; among its primitives, it contains a conditional input operation that tests for presence (or absence) of an output, reminiscent of the inp predicate of Linda. We study three different operational semantics for the output operation, called instantaneous, ordered and unordered. The associated behavioural semantics are obtained as the coarsest congruence contained in the corresponding strong barbed semantics. We prove that when the output operation is instantaneous, the obtained semantics is a sort of asynchronous bisimulation; on the contrary, for the ordered semantics, as well as for the unordered one, the resulting semantics is a small variant of the classic (synchronous) bisimulation. A further result is that the language under unordered semantics is no more Turing powerful, hence the language becomes strictly less expressive. 1 Introduction Generative communication, realized by means of the i...
Some Congruence Properties for πcalculus Bisimilarities
, 1996
"... Both for interleaving and for noninterleaving semantics, several variants of a picalculus bisimilarity can be given which differ on the requirements imposed on name instantiations. Examples are the late, early, open and ground variants. The ground variant is the simplest because it places no requi ..."
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Cited by 6 (0 self)
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Both for interleaving and for noninterleaving semantics, several variants of a picalculus bisimilarity can be given which differ on the requirements imposed on name instantiations. Examples are the late, early, open and ground variants. The ground variant is the simplest because it places no requirements on name instantiations. With the exception of open bisimilarities, none of the bisimilarity considered in the literature is a congruence relation on the full picalculus language. We show that in the case of (certain forms of) causal bisimulation the late, early, open and ground variants coincide and are congruence relations in the sublanguage of the picalculus without matching. We also show that to obtain the same results in the case of the interleaving bisimilarity, in addition to forbidding matching it is necessary to constrain the output prefix.
R.: A theory of “may” testing for asynchronous languages
 LNCS
, 1999
"... Abstract. Asynchronous communication mechanisms are usually at the basis of real distributed systems and protocols. For these systems, asynchronous maybased testing seems to be exactly what is needed to capture safety and certain security properties. We study may testing equivalence focusing on t ..."
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Abstract. Asynchronous communication mechanisms are usually at the basis of real distributed systems and protocols. For these systems, asynchronous maybased testing seems to be exactly what is needed to capture safety and certain security properties. We study may testing equivalence focusing on the asynchronous versions of CCS and picalculus. We start from an operational testing preorder and provide finitary and fully abstract tracebased models for it, together with complete inequational axiomatizations. The results throw light on the differences between synchronous and asynchronous systems and on the weaker testing power of asynchronous observations. 1
Linda based Applicative and Imperative Process Algebras
"... The classical algebraic approach to the specification and verification of concurrent systems is tuned to distributed programs that rely on asynchronous communications and permit explicit data exchange. An applicative process algebra, obtained by embedding the Linda primitives for interprocess com ..."
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Cited by 1 (1 self)
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The classical algebraic approach to the specification and verification of concurrent systems is tuned to distributed programs that rely on asynchronous communications and permit explicit data exchange. An applicative process algebra, obtained by embedding the Linda primitives for interprocess communication in a CCS/CSPlike language, and an imperative one, obtained from the applicative variant by adding a construct for explicit assignment of values to variables, are introduced. The testing framework is used to define behavioural equivalences for both languages and sound and complete proof systems for them are described together with a fully abstract denotational model (namely, a variant of Strong Acceptance Trees). Keywords: Concurrency, Asynchronous Communications, Process Algebras, Formal Semantics. 1
Journal of Automated Reasoning manuscript No.
"... (will be inserted by the editor) Encoding cryptographic primitives in a calculus with polyadic synchronisation ..."
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(will be inserted by the editor) Encoding cryptographic primitives in a calculus with polyadic synchronisation