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74
Decoding Choice Encodings
, 1999
"... We study two encodings of the asynchronous #calculus with inputguarded choice into its choicefree fragment. One encoding is divergencefree, but refines the atomic commitment of choice into gradual commitment. The other preserves atomicity, but introduces divergence. The divergent encoding is ..."
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Cited by 107 (5 self)
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We study two encodings of the asynchronous #calculus with inputguarded choice into its choicefree fragment. One encoding is divergencefree, but refines the atomic commitment of choice into gradual commitment. The other preserves atomicity, but introduces divergence. The divergent encoding is fully abstract with respect to weak bisimulation, but the more natural divergencefree encoding is not. Instead, we show that it is fully abstract with respect to coupled simulation, a slightly coarserbut still coinductively definedequivalence that does not enforce bisimilarity of internal branching decisions. The correctness proofs for the two choice encodings introduce a novel proof technique exploiting the properties of explicit decodings from translations to source terms.
Towards a unified approach to encodability and separation results for process calculi
 Proc. of 19th International Conference on Concurrency Theory (CONCUR’08), number 5201 in LNCS
, 2008
"... Abstract. In this paper, we present a unified approach to evaluating the relative expressive power of process calculi. In particular, we identify a small set of criteria (that have already been somehow presented in the literature) that an encoding should satisfy to be considered a good means for lan ..."
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Cited by 34 (6 self)
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Abstract. In this paper, we present a unified approach to evaluating the relative expressive power of process calculi. In particular, we identify a small set of criteria (that have already been somehow presented in the literature) that an encoding should satisfy to be considered a good means for language comparison. We argue that the combination of such criteria is a valid proposal by noting that: (i) the best known encodings appeared in the literature satisfy them; (ii) this notion is not trivial, because there exist encodings that do not satisfy all the criteria we have proposed; (iii) the best known separation results can be formulated in terms of our criteria; and (iv) some widely believed (but never formally proved) separation results can be proved by using the criteria we propose. Moreover, the way in which we prove known separation results is easier and more uniform than the way in which such results were originally proved. 1
On the Expressive Power of Polyadic Synchronisation in πCalculus
, 2003
"... We extend the πcalculus with polyadic synchronisation, a generalisation of the communication mechanism which allows channel names to be composite. We show that this operator embeds nicely in the theory of πcalculus, we suggest that it permits divergencefree encodings of distributed calculi, and w ..."
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Cited by 33 (9 self)
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We extend the πcalculus with polyadic synchronisation, a generalisation of the communication mechanism which allows channel names to be composite. We show that this operator embeds nicely in the theory of πcalculus, we suggest that it permits divergencefree encodings of distributed calculi, and we show that a limited form of polyadic synchronisation can be encoded weakly in πcalculus. After showing that matching cannot be derived in πcalculus, we compare the expressivity of polyadic synchronisation, mixed choice and matching. In particular we show that the degree of synchronisation of a language increases its expressive power by means of a separation result in the style of Palamidessi's result for mixed choice.
The Probabilistic Asynchronous πCalculus
, 2002
"... In this dissertation, we consider a distributed implementation of the picalculus, more precisely, the version of the picalculus with mixed choice. To this end, we present the probabilistic asynchronous picalculus, which is an extension of the asynchronous picalculus enhanced with a notion of ran ..."
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Cited by 22 (5 self)
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In this dissertation, we consider a distributed implementation of the picalculus, more precisely, the version of the picalculus with mixed choice. To this end, we present the probabilistic asynchronous picalculus, which is an extension of the asynchronous picalculus enhanced with a notion of random choice. We define an operational semantics which distinguishes between probabilistic choice, made internally by the process, and nondeterministic choice, made externally by an adversary scheduler. This distinction will allow us to reason about the probabilistic correctness of algorithms under certain schedulers. We show that in this language we can solve the electoral problem, which was proved not possible in the asynchronous picalculus.
Ensuring termination by typability
 In Proceedings of IFIP TCS 2004
, 2004
"... Abstract. A term terminates if all its reduction sequences are of finite length. We show four type systems that ensure termination of welltyped sscalculus processes. The systems are obtained by successive refinements of the types of the simply typed sscalculus. For all (but one of) the type syste ..."
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Cited by 21 (6 self)
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Abstract. A term terminates if all its reduction sequences are of finite length. We show four type systems that ensure termination of welltyped sscalculus processes. The systems are obtained by successive refinements of the types of the simply typed sscalculus. For all (but one of) the type systems we also present upper bounds to the number of steps welltyped processes take to terminate. The termination proofs use techniques from term rewriting systems. We show the usefulness of the type systems on some nontrivial examples: the encodings of primitive recursive functions, the protocol for encoding separate choice in terms of parallel composition, a symbol table implemented as a dynamic chain of cells. 1 Introduction A term terminates if all its reduction sequences are of finite length. As far as programminglanguages are concerned, termination means that computation in programs will eventually stop. In computer science termination has been extensively investigated in term rewritingsystems [7, 5] and *calculi [9, 4] (where strong normalization is a synonym more commonlyused). Termination has also been discussed in process calculi, notably the
Solos in concert
 IN ICALP’99, LNCS 1644:513–523
, 1999
"... We present a calculus of mobile processes without prefix or summation, and using two different encodings we show that it can express both action prefix and guarded summation. One encoding gives a strong correspondence but uses a match operator; the other yields a slightly weaker correspondence but u ..."
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Cited by 21 (4 self)
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We present a calculus of mobile processes without prefix or summation, and using two different encodings we show that it can express both action prefix and guarded summation. One encoding gives a strong correspondence but uses a match operator; the other yields a slightly weaker correspondence but uses no additional operators.
Electoral systems in ambient calculi
 In Proceedings of 7th International Conference on Foundations of Software Science and Computation Structures, FoSSaCS 2004
, 2004
"... Abstract. This paper compares the expressiveness of ambient calculi against different dialects of the picalculus. Cardelli and Gordon encoded the asynchronous picalculus into their calculus of Mobile Ambients (MA). Zimmer has shown that the synchronous picalculus without choice can be encoded in ..."
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Cited by 18 (6 self)
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Abstract. This paper compares the expressiveness of ambient calculi against different dialects of the picalculus. Cardelli and Gordon encoded the asynchronous picalculus into their calculus of Mobile Ambients (MA). Zimmer has shown that the synchronous picalculus without choice can be encoded in pure (no communication) Safe Ambients. We show that pure MA without restriction has symmetric electoral systems, that is, it is possible to solve the problem of electing a leader in a symmetric network. By the work of Palamidessi, this implies that pure MA without restriction is not encodable (under certain conditions) in the picalculus with separate choice. We adapt the work of Carbone and Maffeis to show that pure MA cannot be encoded (under certain other conditions) into the picalculus with mixed choice (but without matching). 1
On the Expressive Power of Klaimbased Calculi.
 Research report, Dipartimento di Sistemi e Informatica, Universita di Firenze,
, 2004
"... Abstract In this work, we study the expressive power of variants of Klaim, an experimental language with programming primitives for global computing that combines the process algebra approach with the coordinationoriented one. Klaim has proved to be suitable for programming a wide range of distrib ..."
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Cited by 16 (9 self)
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Abstract In this work, we study the expressive power of variants of Klaim, an experimental language with programming primitives for global computing that combines the process algebra approach with the coordinationoriented one. Klaim has proved to be suitable for programming a wide range of distributed applications with agents and code mobility, and has been implemented on the top of a runtime system based on Java. The expressivity of its constructs is tested by distilling from it some (more and more foundational) calculi and studying the encoding of each of the considered languages into a simpler one. An encoding of the asynchronous πcalculus into one of these calculi is also presented.