U. Nestmann. What is a `good' encoding of guarded choice? Information and Computation, 156:287--319, 2000. 23  Home/Search   Document Not in Database   Summary   Related Articles   Check

....So far, only the so called asynchronous subset has been implemented [8] In [7] the second author has shown that the full calculus is strictly more expressive than its asynchronous subset, and, more in general, that there is no hope of implementing the calculus with deterministic methods. In [6] Nestmann has shown that the gap in expressive power, and the difficulty in the implementation with deterministic methods, is due to the mixed (input and output) guarded choice construct of the calculus. Such mechanism, however, would be very desirable as it provides a powerful programming ....

U. Nestmann. What is a `good' encoding of guarded choice? In C. Palamidessi and J. Parrow, editors, Proceedings of EXPRESS '97: Expressiveness in Concurrency (Santa Margherita Ligure, Italy, September 8--12, 1997.

....Uniform essentially means homomorphic with respect to the parallel and the renaming operators, and reasonable means sensitive to the capability of achieving success in all possible computations. The additional expressive power is due exactly to the mixed choice construct, as shown by Nestmann [29]. The motivation for this work comes from the observation that the # calculus, and the formalisms that are based on synchronous communication and contain a guarded choice operator, are di#cult to implement in an entirely distributed way with nonprobabilistic methods. The combination of ....

....P can make two transitions P , then there exists P # such that P P # and P P # . Figure 2.1 shows the behavior of a confluent process P . P P P 1 P 2 xz xv xv xz Fig. 2.1. The confluence property for a process P 17 Another remarkable result was proved by Nestmann in [29]. Nestmann has been shown that the additional expressive power is due exactly to the mixed choice construct since the # calculus with separate choices can be encoded in the asynchronous # calculus. Nestmann s encoding of separate choices is an extension of the encoding of input guarded choice of ....

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Uwe Nestmann. What is a `good' encoding of guarded choice? In Catuscia Palamidessi and Joachim Parrow, editors, Proceedings of EXPRESS '97: Expressiveness in Concurrency (Santa Margherita Ligure, Italy, September 8--12, 1997.

....that is choice, among just input guarded agents, and recursive de nitions can be encoded in the asynchronous pi calculus. When general choice is involved, the situation becomes more complex, and it turns out that there is no satisfactory encoding of general choice in the asynchronous pi calculus [13, 11]. Below 9 ; x : x : f : Exp[Con( 1 ; n ) t i : Exp[ i ] f(t 1 ; t n ) Exp[ 0 : Proc p : Proc p : Proc p j q : Proc ; x : Exp[Ch( p : Proc new x : in p : Proc a : Exp[Ch( x : Exp[ p : Proc a(x) p : Proc a : Exp[Ch( ....

U. Nestmann. What is a `good' encoding of guarded choice? In C. Palamidessi and J. Parrow, editors, EXPRESS '97: Expressiveness in Concurrency (Santa Margherita Ligure, Italy, September 8-12, 1997), volume 7 of ENTCS. Elsevier Science Publishers, 1997.

....Our system can be enhanced in many ways: The syntax of processes could be enriched by adding the choice construct ( and recursive denitions to our language; this would require the adaption of our methods to the extended language. We may alternatively choose to use well known encodings [Nes97, Mil91], which would compel the user to work only with weak bisimilarity. The size of the relations could be reduced by enriching structural congruence with additional laws (e.g. x = 2 n(ff) x) ff:P j ff: x) P ) and 21 adapting our normalisation algorithm, as well as by considering other up to ....

U. Nestmann. What is a `good' encoding of guarded choice? In Proceedings of EXPRESS'97, volume 7 of ENTCS, 19997.

....Bit Protocol 4.2 The Encodings Discussion Choice To model the alternating bit protocol in our system, we have to deal with two constructs that are not present in our language, namely operators on booleans and the choice operator. Well known encodings of these constructs exist (see [Mil91,Nes97]) these encodings belong to theoretical studies, and have been mechanised e.g. in the programming language PICT [PT97] We shall see 3 The language we use here is actually value passing CCS; for the encodings discussed below, however, we shall need the full power of calculus. here the ....

....use here is actually value passing CCS; for the encodings discussed below, however, we shall need the full power of calculus. here the problems that arise as we try to use them in the context of veri cation, and how they can be treated. Various encodings of guarded choice are investigated in [NP96,Nes97]; the general idea is to represent each branch of the choice by a parallel component, and to implement a lock mechanism to prevent other branches to re when one branch has committed. In general, once a choice has been taken, the dead branches remain, and, depending on the encoding we choose, ....

U. Nestmann. What is a `good' encoding of guarded choice? In Proceedings of EXPRESS'97, volume 7 of ENTCS, 1997.

....abstract (up to congruence) while in (ii) we have only adequate encodings from the right calculus to the left one. Palamidessi s result [40] is stronger than (iii) above because the condition (3) in Definition 5.1 is not required to prove the separation between P 1 and P 2 . See Introduction in [38] for the detailed relationship about adequacy and full abstraction between existent encodings. 6.2.1. Local calculus. Two remarks are due for Proposition 5.6 (1) concerning local calculus. First, in [5] Boreale recently established an interesting result which shows power of the local ....

Nestmann, U., What is a `Good' Encoding of Guarded Choice? Proc. of Express'97, Vol 7, ENTCS, Elsevier Science Publishers, 1997.

....that is choice, among just input guarded agents, and recursive definitions can be encoded in the asynchronous pi calculus. When general choice is involved, the situation becomes more complex, and it turns out that there is no satisfactory encoding of general choice in the asynchronous pi calculus [17, 15]. Below we will present an adequate encoding into Lpi of an explicitly typed variant of the synchronous pi calculus, featuring data structures in the form of freely constructed terms, general (mixed) choice, a pattern matching case construct and exceptions signals. 4.1 Basic Typed Synchronous ....

U. Nestmann. What is a `good' encoding of guarded choice? In C. Palamidessi and J. Parrow, editors, EXPRESS '97: Expressiveness in Concurrency (Santa Margherita Ligure, Italy, September 8--12, 1997), volume 7 of ENTCS. Elsevier Science Publishers, 1997.

....into CCS preserving a reasonable Supported by the British Council, the Consiglio Nazionale delle Ricerche, and the Staff Exchange Scheme of the European Commission s ERASMUS programme. y Supported by the European Commission s HCM programme and NSERC of Canada. semantics. Nestmann [Nes97] showed that either the uniformity of the encoding or the reasonableness of the semantics is necessary for Palamidessi s other 1 negative result. In this paper, we present a compositional, yet not uniform , encoding of the calculus into CCS. We follow the scheme proposed by Sangiorgi in ....

U. Nestmann. What is a `Good' Encoding of Guarded Choice? In C. Palamidessi and J. Parrow, editors, Proceedings of EXPRESS'97, volume 7 of Electronic Notes in Theoretical Computer Science, Santa Margherita Ligure, September 1997. Elsevier.

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U. Nestmann. What Is a `Good' Encoding of Guarded Choice? In C. Palamidessi and J. Parrow, eds, Proceedings of EXPRESS '97, volume 7 of ENTCS. Elsevier Science Publishers, 1997.

....in [Pal97] that it is not possible to give a divergence free encoding of mixed guarded choice in a fully distributed way, i.e. where parallel composition and restriction do not add centralizing components that could be used to globally manage the interactions on channels. Nestmann showed in [Nes97] that it is, however, possible to encode separate choice (either purely input guarded or purely output guarded) up to Palamidessi s criteria. Furthermore, the latter contains a discussion on how to relax the criteria for full distribution to get al..so good encodings for mixed choice along the ....

U. Nestmann. What Is a `Good' Encoding of Guarded Choice? In C. Palamidessi and J. Parrow, eds, Proceedings of EXPRESS '97, volume 7 of ENTCS. Elsevier Science Publishers,

....showed in [Pal97] that it is not possible to give a divergence free encoding of mixed guarded choice in a fully distributed way, i.e. where parallel composition and restriction do not add centralizing components that could be used to globally manage the interactions on channels. Nestmann showed in [Nes97] that it is, however, possible to encode separate choice (either purely input guarded or purely output guarded) up to Palamidessi s criteria. Furthermore, the latter contains a discussion on how to relax the criteria for full distribution to get al..so good encodings for mixed choice along the ....

U. Nestmann. What Is a `Good' Encoding of Guarded Choice? In Proceedings of EXPRESS '97, 1997. To appear.

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U. Nestmann. What is a `good' encoding of guarded choice? Information and Computation, 156:287--319, 2000. 23

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U. Nestmann. What is a `good' encoding of guarded choice? Journal of Information and Computation, 156:287--319, 2000.

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Uwe Nestmann. What is a `good' encoding of guarded choice? Journal of Information and Computation, 156:287--319, 2000.

No context found.

Uwe Nestmann. What is a `good' encoding of guarded choice? In Catuscia Palamidessi and Joachim Parrow, editors, Proceedings of EXPRESS '97: Expressiveness in Concurrency (Santa Margherita Ligure, Italy, September 8--12, 1997.

No context found.

Uwe Nestmann. What is a `good' encoding of guarded choice? In Catuscia Palamidessi and Joachim Parrow, editors, Proceedings of EXPRESS '97: Expressiveness in Concurrency (Santa Margherita Ligure, Italy, September 8--12, 1997.

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Uwe Nestmann. What is a `good' encoding of guarded choice? Technical report, BRICS, 1997.

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Uwe Nestmann. What is a `good' encoding of guarded choice? Technical report, BRICS, 1997.

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Uwe Nestmann. What is a `good' encoding of guarded choice? In Catuscia Palamidessi and Joachim Parrow, editors, Proceedings of EXPRESS '97: Expressiveness in Concurrency (Santa Margherita Ligure, Italy, September 8--12, 1997.

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