U. Nestmann and B. C. Pierce. Decoding choice encodings. Journal of Information and Computation, 163:1--59, 2000.  Home/Search   Document Details and Download   Summary   Related Articles   Check

.... calculus we have chosen. Our processes belong to a polyadic (in the sense that many names can be transmitted in a single communication) and sum free calculus; both polyadic communications and the sum operator (also called choice operator) can be encoded into a monadic, sum free calculus (see [Mil91, NP96]) While sum can be useful from a theoretical point of view to build axiomatisations, it turns out that it can be discarded without much loss of convenience for implementation tasks. Polyadicity, on the other hand, is a very useful feature when taken as primitive, because it makes the treatment of ....

U. Nestmann and B. C. Pierce. Decoding choice encodings. In Proceedings of CONCUR '96, number 1119, August 1996.

....stronger it is, the more confidence we gain that the encoding is correct. At first glance, one might take some form of weak bisimulation since (modulo divergence) it is finer than most notions of testing [dH84, Sew97] and is easier to work with. However, as in Nestmann s work on choice encodings [NP96] would not hold, as the encoding [ P ] involves partial commitment of some nondeterministic choices. An example is given in 6. We therefore take to be an adaptation of coupled simulation [PS92] to our language. This is a slightly coarser relation, but it is expected to be finer than ....

....new # in in in (LP LQ) # new new new # in in in LQ # . Intuitively, the first premise (LP #,# LP # ) of the theorem must allow all the potential agent movements of LQ and LQ # , and symmetrically. Expansion To construct the coupled simulation, we use an expansion relation [NP96] and the up to technique of [SM92] adapted with translocation, to allow elimination of target processes that are in intermediate housekeeping stages. The definitions are omitted. We depend on a congruence result, analogous to that above, for expansion. Temporary Immobility At many points in ....

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Uwe Nestmann and Benjamin C. Pierce. Decoding choice encodings. [CON96], pages 179--194.

....f means that it has been decided. Notice that the symmetry is broken exactly when one process succeeds in performing both inputs. In the algorithm we make use of the if then else construct, which is defined by the structural rules if t then P else Q j P if f then P else Q j Q As discussed in [8], these features (booleans and if then else) can be translated into the asynchronous calculus, and therefore in pa . Correctness of the algorithm We prove now that the algorithm is correct, namely that the probability that a leader is eventually elected is 1 under every scheduler. In the ....

Uwe Nestmann and Benjamin C. Pierce. Decoding choice encodings. In Ugo Montanari and Vladimiro Sassone, editors, Proceedings of CONCUR '96: Concurrency Theory (7th International Conference, Pisa, Italy, August 1996), volume 1119 of Lecture Notes in Computer Science, pages 179--194. Springer-Verlag, 1996. Full version to appear in Information and Computation.

....one of the suspended operations is nondeterministically selected to proceed; in the latter case, one of the matching tuples is arbitrarily chosen. Hence, within the reduced language, nondeterminism can be modelled via the pattern matching mechanism; but it could also be retrieved like, e.g. in [31]. There are several process calculi using explicit localities. For instance, localities in D# [25] model distribution and mobility of # calculus processes. In the distributed Join calculus [21] another variant of # calculus, channels have a unique locality and agents may move from a locality to ....

U. Nestmann, B.C. Pierce, Decoding choice encodings, in: U. Montanari, V. Sassone (Eds.), CONCUR'96, Proc., Lecture Notes in Computer Science, vol. 1119, Springer, Berlin, 1996, pp. 179--194.

....model with a lossy communication medium. The availability of ahbi only depends on whether the other summand c(x) P can perform its input at c. An asynchronous process that non deterministically can chose to send ahbi or to receive at c(x) P should be written . ahbi c(x) P . Pierce and Nestmann [27] have showed that this form of choice, in which each summand is guarded by a or by an input prex, can be encoded in the asynchronous calculus. Their encoding can also be written in L. 12 2.5.2 Output capability One of the most important application areas for the calculus is object oriented ....

.... calculus) the loss of the axiomatisations of the ordinary calculus [29] 13 2.5. 5 Consequences of the constraints on the expressiveness Various encodings have been given that show that the loss of expressiveness moving from calculus to the asynchronous calculus and then to L is limited [27, 5, 17, 7] and in any case acceptable in a model of asynchronous communications. Palamidessi [28] has shown that the general choice operator of the calculus cannot be encoded in an asynchronous calculus, by proving that the symmetric leader election problem cannot be solved in a calculus without choice. ....

U. Nestmann and B. Pierce. Decoding choice encodings. In Proc. CONCUR '96, volume 1119 of Lecture Notes in Computer Science. Springer Verlag, 1996.

....corresponds to the simultaneous exchange of information between two partners. For several years there have been di#erent opinions regarding the expressiveness of asynchronous communication. The encodings of Honda Tokoro [14] and Boudol [5] for the output prefix and of Nestmann Pierce [32] for the input prefix partially legitimated the idea that the two communication mechanisms are equivalent. However, the full # calculus, and process algebras with synchronous communication in general, have a mixed choice mechanism, i.e. choice of prefixed processes where the prefixes can be ....

....of a non output choice construct, namely a summation of processes prefixed with # or input actions. Actually, 1] considers a binary non output sum operator instead of a n ary one, but under the assumption that the binary sum is commutative and associative, the two definitions coincide. Thanks to [32], we know that this construct does not increase the expressive power. In [32] it is shown that the asynchronous # calculus with input guarded choice can be encoded into its choice free fragment. It is easy to extend the encoding to include also # prefixes. The asynchronous # calculus (# ....

[Article contains additional citation context not shown here]

Uwe Nestmann and Benjamin C. Pierce. Decoding choice encodings. In Ugo Montanari and Vladimiro Sassone, editors, Proceedings of CONCUR '96: Concurrency Theory (7th International Conference, Pisa, Italy, August 1996.

....T for short. We make use of the correctness results for the pik calculus to leverage a correctness proof for the atf calculus. We do this by first giving a translation from the atf calculus to the pik calculus, that preserves and reflects log consistency. We then show operational correspondence [39]: a reduction by a transaction in the atf calculus can always be matched by a number of reductions of that transaction s translation. Theorem 1 verifies that reductions in the pik calculus preserve log consistency. Therefore if the original transaction in the atf calculus is consistent, then any ....

Uwe Nestmann and Benjamin C. Pierce. Decoding choice encodings. In Ugo Montanari and Vladimiro Sassone, editors, CONCUR '96: Concurrency Theory, 7th International Conference, volume 1119, pages 179--194, Pisa, Italy, 1996. Springer-Verlag. Also BRICS Technical Report RS-99-42.

....cannot be used as a communication channel at the net level, even though they are known by both the client and the server processes. Without any pretence of completeness: the literature is rich with expressivity results on di#erent fragments of the # calculus. In particular, we refer the reader to [24,23,17,18,19] 12 Client = #c) w#finger , c# c(x) print#x#) Server = w(s, r) s#r# finger(y) y#wUsers# daytime(z) z#wDate# System = net [host [Client ] host [Server ] Declarations = finger host , daytime host , print host , c net , w net An encoding of la# in # calculus is given in [10] ....

Nestmann, U. and B. C. Pierce, Decoding choice encodings, Journal of Information and Computation 163 (2000), pp. 1--59.

....language. 1 Introduction The asynchronous calculus [5, 9] is a very simple but powerful formalism for describing distributed and mobile processes, based on the asynchronous exchange of names. Its descriptive power as a programming calculus has been demonstrated theoretically in papers such as [5, 9, 10, 13] and practically in [14] where a minor variant takes the role of the target implementation language for the sophisticated distributed and higher order programming language Pict. However a calculus should not only be computationally expressive. The most successful process calculi, such as CCS ....

U. Nestmann and B. Pierce. Decoding choice encodings. In Proc. CONCUR'96, LNCS 1119, 1996.

....gaining momentum is that concerned with the semantics of programs. In this community one is often interested in comparing calculi. Certain translations turn out to be fully abstract in an asynchronous setting, where the observer has less power. Examples include the encoding of input guarded choice [15] into the asynchronous calculus, and the encoding of the asynchronous calculus into the join calculus [6] A way to restrict a process calculus to asynchronous communications is to remove output prexing. In other terms, an asynchronous output a followed by a process P is the same as the ....

....Forms of asynchronous calculus have also been studied in [7] but the bisimilarity used is the standard (synchronous) one. Part of our theory, in particular axioms and normal forms, is based on that in [7] Our formulation of asynchronous bisimulation has been recently used by Nestmann and Pierce [15] to prove the full abstraction of the above mentioned encoding of input guarded choice. The paper is organized as follows. In section 2 we provide the basic denitions. In section 3 we present various characterizations and properties of strong asynchronous bisimulation. In section 4 we ooeer a ....

U. Nestmann and B. Pierce. Decoding choice encodings. In CONCUR 96, Springer Lect. Notes in Comp. Sci. 1119, Pisa, 1996.

....a reaction rule of the form x#y# x(z) a y z a x(z) a . This is a commonly done in asynchronous variations of # calculus [HT91] Another way of handling replication is via an encoding in terms of combinators (already mentioned above) HY94b] For input guarded summation, encoding [NP96] is also an option. full reflexion: The contexts considered in Chapter 5 have only a limited form of reflexion, as enforced by the condition Loose that prevents tight loops linking a hole to itself. This simplifying assumption makes the composition of contexts and the composition of the ....

U. Nestmann and B. C. Pierce. Decoding choice encodings. In CONCUR '96, Concurrency Theory, 7th International Conference, Pisa, Italy, August 26--29,

....one of the suspended operations is nondeterministically selected to proceed; in the latter case, one of the matching tuples is arbitrarily chosen. Hence, within the reduced language nondeterminism can be modelled via the pattern matching mechanism; but it could also be retrieved like, e.g. in [31]. There are several process calculi using explicit localities. For instance, localities in D [25] model distribution and mobility of calculus processes. In the distributed Join calculus [21] another variant of calculus, channels have a unique locality and agents may move from a locality to any ....

U. Nestmann, B.C. Pierce. Decoding Choice Encodings. CONCUR'96, Proceedings (U.Montanari, V.Sassone, Eds.), LNCS 1119, pp. 179-194, Springer, 1996.

....write primitives are sufficiently expressive for solving the coordination between (probably infinite state) application programs. Our construction has similarities with transformations in [18] where a requirements specification is split in parallel parts communicating via message passing, and [20], where an encoding of choice in the a synchronous calculus is provided. Both papers introduce internal loops to resolve external choices, similar to our translation. However, those papers are based on event based coordination, whereas our approach uses a persistent data approach. For this ....

U. Nestmann and B.C. Pierce. Decoding choice encodings. In U. Montanari and V. Sassone, editors, Proc. of the 7th Int. Conf. on Concurrency Theory (CONCUR 96), number 1119 in LNCS, pages 179--194. Springer-Verlag, 1996.

....The stronger it is, the more con dence we gain that the encoding is correct. At rst glance, one might take some form of weak bisimulation since (modulo divergence) it is ner than most notions of testing [dH84, Sew97] and is easier to work with. However, as in Nestmann s work on choice encodings [NP96] y) would not hold, as the encoding C [ P ] involves partial commitment of some nondeterministic choices. An example is given in x6. We therefore take to be an adaptation of coupled simulation [PS92] to our language. This is a slightly coarser relation, but it is expected to be ner than any ....

....(LP j LQ) M new new new in in in LP 0 j LQ 0 : Intuitively, the rst premise (LP M P ; LP 0 ) of the theorem must allow all the potential agent movements of LQ and LQ 0 , and symmetrically. Expansion To construct the coupled simulation, we use an expansion relation [NP96] and the up to technique of [SM92] adapted with translocation, to allow elimination of target processes that are in intermediate housekeeping stages. The de nitions are omitted. We depend on a congruence result, analogous to that above, for expansion. Temporary Immobility At many points in ....

[Article contains additional citation context not shown here]

Uwe Nestmann and Benjamin C. Pierce. Decoding choice encodings. [CON96], pages 179-194.

....virtual machine to have active states that do not have a direct equivalent in the atomic machine. Coupled simulation has been used before in cases where bisimulation is too strong, e.g. in [23] to establish correctness of a distributed implementation of multi party synchronisation, and in [22] to define correctness of choice encodings. Last but not least, approaches similar to ours have been worked out in related research areas. While of necessity remaining very incomplete, we would like to mention again the work on atomic transactions in [19] as well as insights in atomicity to be ....

U. Nestmann and B. Pierce. Decoding choice encodings. In U. Montanari and V. Sassone, eds., Concur '96: Concurrency Theory, vol. 1119 of Lecture Notes in Computer Science, pp. 179--194. Springer-Verlag, 1996.

....encodable in a choice free calculus for example a purely internal choice can be encoded in the calculus given in Section 1. 1 above by [ P Q] def = new c in (cx j cx:P j cx:Q) c; x not free in P; Q but in other cases non encodability results can be proved (see work of Nestmann and Pierce [NP96] and of Palamidessi [Pal97] Asynchrony The calculus of Section 1.1 is asynchronous it has only a bare output cv as opposed to an output pre x cv:P that starts P when the output has been received. Again, for programming it seems that pre xing (or synchronous) output can be uncommon; it can ....

Uwe Nestmann and Benjamin C. Pierce. Decoding choice encodings. In Proceedings of CONCUR '96, LNCS 1119, pages 179-194, August 1996.

....mo mentum is that concerned with the semantics of programs. In this community one is often interested in comparing calculi. Certain translations turn out to be fully abstract in an asynchronous setting, where the observer has less power. Examples include the encoding of input guarded choice [NP96] into the asynchronous calculus and the encoding of the asynchronous calculus into the join calculus [FG96] A way to restrict a process calculus to asynchronous communications is to remove output prexing. In other terms, an asynchronous output a followed by a process P is the same as the ....

.... calculus have also been studied in [HKH95] but the bisimilarity used is the standard (synchronous) one. Part of our theory, in particular axioms and normal forms, is related to that in [HKH95] Our formulation of asynchronous bisimulation has been recently used by Nestmann and Pierce [NP96] to prove the full abstraction of the above mentioned encoding of input guarded choice. The paper is organized as follows. In section 2 we provide the basic denitions. In section 3 we present various characterizations and properties of strong asynchronous bisimu lation. In section 4 we study an ....

U. Nestmann and B. Pierce. Decoding choice encodings. In CONCUR 96, SLNCS to appear, Pisa, 1996.

....encodable in a choice free calculus for example a purely internal choice can be encoded in the calculus given in section 1. 1 above by [ P Q] def = new c in (cx j cx:P j cx:Q) c; x not free in P; Q but in other cases non encodability results can be proved (see work of Nestmann and Pierce [NP96] and of Palamidessi [Pal97] Asynchrony The calculus of section 1.1 is asynchronous it has only a bare output cv as opposed to an output pre x cv:P that starts P when the output has been received. Again, for programming it seems that pre xing (or synchronous) output can be uncommon; it can ....

Uwe Nestmann and Benjamin C. Pierce. Decoding choice encodings. In Proceedings of CONCUR '96, LNCS 1119, pages 179-194, August 1996.

....and trivial tests, is close to the asynchronous pi calculus [2, 7] However, the full pi calculus as presented in [10] besides synchronous output, also includes further useful control combinators, like general choice, name matching, and a standard scheme of de ning agents recursively. It is known [2, 12] that synchronous output, input only choice, 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 ....

....in Lpi. We will not attempt to present here any formal proof of correctness of the above encodings; this will be carried out elsewhere. Basically, we will show that the encoding of 2 is fully abstract when one takes for process equivalences a notion of weak barbed coupled simulation adapted from [14, 12]. The reason why weak barbed bisimulation is not adequate is because while the triggering of an exception and the corresponding collapse of the embedded process is atomically performed in 2, the Lpi translation simulation is realized in a gradual and delayed fashion. 19 3.4 Functions and ....

U. Nestmann and B. C. Pierce. Decoding choice encodings. In U. Montanari and V. Sassone, editors, CONCUR '96: Concurrency Theory (7th International Conference, Pisa, Italy, August 1996, Proceedings), volume 1119 of Lecture Notes in Computer Science, pages 179-194. sv, 1996.

....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, ....

....syntactically, to prevent our relation from growing. We have chosen to encode the binary choice of Figure 4 as follows ( represents the encoding function) a(x) P b(y) Q] def = l) l j a(x) l:b(x) P j b(y) l:a(y) Q) This encoding represents an adaptation of those described in [NP96]; here, a lock channel l is created and when one branch is chosen, it deactivates the other branch by consuming its head pre x, thus leading to a subterm of the form ( l) l:T ) that can immediately be garbage collected using the additional law for structural congruence (see Section 1) Our ....

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U. Nestmann and B. C. Pierce. Decoding choice encodings. In Proceedings of CONCUR '96, number 1119. LNCS, Springer Verlag, August 1996.

.... mobile calculi are [17, 19, 15, 4] In these theories, the most important algebraic law that is not in the theory of the synchronous calculus is a(x) ax = 0 Although this law is useful (it is used for instance by Pierce and Nestmann to prove the correctness of an encoding of guarded sum [29]) it seems fair to say the restriction to asynchronous contexts does not aoeect much barbed congruence. By contrast, asynchrony has strong semantic consequences under of simpli cations (a) and (b) Consider these laws: ab = c) ac j c . b) where c . b def = c(x) bx and c 6= b (1) ab j c . ....

U. Nestmann and B. Pierce. Decoding choice encodings. In Proc. CONCUR '96, volume 1119 of Lecture Notes in Computer Science. Springer Verlag, 1996.

....p or p 0 is performed whether x = y or not. A weaker operator is namematching that has no continuation in case of disequalities. We write the name matching as a derived operator: x = y] p; 0. Name comparisons will make easy the encoding of inheritance mechanisms in our basic calculus. See [NP96] for an analysis of the expressiveness of name comparison in process algebras. 1.2.2 Semantics The operational semantics is defined as a reflexive chemical abstract machine rcham, for short in the style of [FG96] The chemical rules are given in Table 1.1. They define disjoint sets of ....

U. Nestmann and B. C. Pierce. Decoding choice encodings. In CONCUR '96: Proceedings of the 7th International Conference on Concurrency Theory, volume 1119 of Lecture Notes in Computer Science, pages 179--194. Springer-Verlag, 1996.

....Output guarded choice is traditionally disallowed in asynchronous process calculi. This is in accordance with the results of this paper, since output guarded 14 choice violates the two asynchronous principles of output determinacy and output confluence. For the calculus, Nestmann and Pierce [13] have recently shown that input guarded choice can be encoded from the other constructs; hence they include it in their version of the asynchronous calculus, and we include it here for asynchronous CCS as well. Assume a set of defining equations A def =P , one for each process constant A. The ....

U. Nestmann and B. C. Pierce. Decoding choice encodings. In CONCUR '96, Springer LNCS 1119, pages 179--194, 1996.

.... [7, 19] 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 [32] and input guarded summations [37]. The present paper shows that each of the five basic combinators introduced in [22] 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 semantic equalities. Expressive power of several interesting ....

.... On the other hand, without match or summation, the output prefixless monadic calculus [19, 13, 21, 7, 3] is known as a powerful formalism to represent a wide repertoire of interactive computational structures: polyadic and synchronous communications [19, 7] and even input guarded summations [37] are embeddable within this calculus. At the practical level, this expressiveness gives rise to a useful high level concurrent programming language Pict [45] which is built on the polyadic version of this calculus with a strong typing system. At the semantic level, there exists a theory of ....

[Article contains additional citation context not shown here]

Nestmann, U. and Pierce, B., Decoding choice encodings, Proc. CONCUR'96, LNCS 1119, pp.179--194, Springer-Verlag, 1996.

.... operator [13, 6] 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 name passing [19] and input guarded summations [22]. The present paper shows that each of five basic combinators introduced in [15] 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 ....

....world. On the other hand, without match or summation, the output prefixless calculus [13, 9, 14, 6, 3] is known as a powerful formalism to represent a wide repertoire of interactive computational structures: polyadic and synchronous communications [13, 6] and even input guarded summations [22], are embeddable within this calculus. At the practical level, this expressiveness gives rise to a useful high level concurrent programming language Pict [28] which is basically built on the polyadic version of this calculus with a strong typing system. At the semantic level, there exists a ....

[Article contains additional citation context not shown here]

Nestmann, U. and Pierce, B., Decoding choice encodings, Proc. CONCUR'96, LNCS 1119, pp.179-- 194, Springer-Verlag, 1996.

.... [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 ....

.... On the other hand, without match or summation, the output prefixless monadic calculus [16, 11, 17, 7, 3] is known as a powerful formalism to represent a wide repertoire of interactive computational structures: polyadic and synchronous communications [16, 7] and even input guarded summations [26], are embeddable within this calculus. At the practical level, this expressiveness gives rise to a useful high level concurrent programming language Pict [33] which is basically built on the polyadic version of this calculus with a strong typing system. At the semantic level, there exists a ....

[Article contains additional citation context not shown here]

Nestmann, U. and Pierce, B., Decoding choice encodings, Proc. CONCUR'96, LNCS 1119, pp.179-- 194, Springer-Verlag, 1996.

.... Hence, within the reduced language non7 fig v Pi frg 1 2 2 v Pi 1 1 v Pi 0 1 2 v Pi 0 2 ( 1 [ 2 ) v Pi ( 0 1 [ 0 2 ) Table 2: Subpolarity Rules determinism can be modelled via the pattern matching mechanism; but it could also be retrieved like, e.g. in [34]. There are several process calculi using explicit localities for modelling distribution and mobility. For instance, in the Join calculus [24] channels have a unique location and agents may move from a location to any other location. Amadio [4] has shown that a fragment of the asynchronous ....

U. Nestmann, B.C. Pierce. Decoding Choice Encodings. CONCUR'96, Proceedings (U.Montanari, V.Sassone, Eds.), LNCS 1119, pp. 179-194, Springer, 1996.

....replicated prefixes ff 1 : ff 2 : ff 3 up to weak open equivalence [18] He also shows that duos, i.e. prefixes nested to depth 2, are not sufficient. In this paper we show that for the fusion calculus, it suffices with solos, i.e. we do not need prefixes at all. Nestmann and Pierce show in [10] that input guarded choice P i u i ( e x i ) P i can be encoded in the asynchronous calculus without choice, up to coupled bisimulation [14] and in [9] Nestmann gives encodings of separate and mixed guarded choice. While these encodings involve increasingly complex communication protocols, ....

U. Nestmann and B. C. Pierce. Decoding choice encodings. In U. Montanari and V. Sassone, editors, Proc. of CONCUR '96, volume 1119 of LNCS, pages 179--194. Springer, 1996.

No context found.

U. Nestmann and B. C. Pierce. Decoding Choice Encodings. In Proceedings of CONCUR '96, volume 1119 of LNCS, pages 179--194. Springer, 1996.

No context found.

U. Nestmann and B. C. Pierce. Decoding Choice Encodings. In U. Montanari and V. Sassone, eds, Proceedings of CONCUR '96, volume 1119 of LNCS, pages 179--194. Springer, 1996.

....wz can reduce spontaneously to wy. In Pict we go a step further, dropping the choice operator altogether. This simplifies both formal semantics and implementation, and has little effect on the expressiveness of the language, since input only choice is easy to implement as a library module [PT95, NP96] This has some cost in syntactic convenience, and some benefit in flexibility. Our library actually implements a subset of Reppy s events [Rep91] allowing the branches of a choice to be manipulated as data. In fact, most Pict programs use simpler mechanisms 3 such as locks and semaphores ....

Uwe Nestmann and Benjamin C. Pierce. Decoding choice encodings. Technical report, University of Cambridge and University of Erlangen-Nuernberg, April 1996.

....# calculus [Bou92] have recently attracted particular interest, since they still have surprisingly expressive power. To study their expressiveness relative to the original # calculus [MPW92] the existence of good encodings of operators for synchronous output and guarded choice = [NP96] C A [Bou92, Hon92] aa C C . identity embedding : uniform fully abstract : uniform reasonable : impossible Figure 1: Encodings for choice and synchrony in the asynchronous # calculus (we are not concerned with matching operators) is ....

....logic. Choice operators play a crucial role in assessing the expressiveness of the original (synchronous) # calculus and its asynchronous descendants, since they are usually present in the former, but not [HT92, Bou92] or only restricted [ACS98] in the latter. Nestmann and Pierce showed in [NP96] that at least input guarded choice can be encoded into # a and proven to be fully abstract with respect to weak bisimulation [HT92, ACS98] for an encoding with infinite loops, and fully abstract with respect to coupled simulation for a divergence free encoding. However, Palamidessi proved that ....

[Article contains additional citation context not shown here]

U. Nestmann and B. C. Pierce. Decoding Choice Encodings. In U. Montanari and V. Sassone, eds, Proceedings of CONCUR '96, volume 1119 of LNCS, pages 179--194. Springer,

....and guarded choice (we are not concerned with matching operators) is investigated. Figure 1 summarizes the respective results that are known from the literature, on which we comment in the following paragraphs. The subscripts a and s denote calculi with asynchronous and ffi = [NP96] C s A [Bou92, Hon92] aaC C ffi : identity embedding : uniform fully abstract : uniform reasonable : impossible Figure 1: Encodings for choice and synchrony in the asynchronous calculus synchronous output, respectively, whereas the ....

....logic. Choice operators play a crucial role in assessing the expressiveness of the original (synchronous) calculus and its asynchronous descendants, since they are usually present in the former, but not [HT92, Bou92] or only restricted [ACS96] in the latter. Nestmann and Pierce showed in [NP96] that at least input guarded choice can be encoded into a and proven to be fully abstract with respect to weak bisimulation [HT92, ACS96] for an encoding with infinite loops, and fully abstract with respect to coupled simulation for a divergence free encoding. However, Palamidessi proved that ....

[Article contains additional citation context not shown here]

U. Nestmann and B. C. Pierce. Decoding Choice Encodings. In U. Montanari and V. Sassone, editors, Proceedings of CONCUR '96, volume 1119 of LNCS, pages 179--194. Springer,

....between different calculi, since it rests on laxer notions of observation. Also, a barbed definition of coupled simulation, based on reduction semantics, might allow to prove results for encodings which are not fully abstract up to weak bisimulation. Since the writing of the conference version [NP96] of this paper, new results have been presented concerning more sophisticated choice operators and their encodings. Palamidessi 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 ....

U. Nestmann and B. C. Pierce. Decoding Choice Encodings. In U. Montanari and V. Sassone, editors, Proceedings of CONCUR '96, volume 1119 of LNCS, pages 179--194. Springer, 1996.

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U. Nestmann and B. C. Pierce. Decoding choice encodings. Journal of Information and Computation, 163:1--59, 2000.

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U. Nestmann, B. C. Pierce, Decoding choice encodings, in: U. Montanari, V. Sassone (Eds.), CONCUR '96: Concurrency Theory, 7th International Conference, Vol. 1119, Springer-Verlag, Pisa, Italy, 1996, pp. 179--194.

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U. Nestmann and B. Pierce. Decoding choice encodings. In CONCUR 96, Springer Lect. Notes in Comp. Sci. 1119, Pisa, 1996.

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U. Nestmann and B. Pierce. Decoding choice encodings. In Proc. CONCUR '96, volume 1119 of LNCS. Springer Verlag, 1996.

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U. Nestmann and B. C. Pierce. Decoding choice encodings. Journal of Information and Computation, 163:1--59, 2000.

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U. Nestmann and B. C. Pierce. Decoding choice encodings. In U. Montanari and V. Sassone, editors, 7th International Conference on Concurrency Theory (CONCUR '96), volume 1119 of LNCS, pages 179-194. Springer-Verlag, Aug. 1996. Revised full version as report ERCIM-10/97-R051, 1997.

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Uwe Nestmann and Benjamin C. Pierce. Decoding choice encodings. Journal of Information and Computation, 163:1--59, 2000.

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U. Nestmann and B. Pierce. Decoding choice encodings. In Proc. of CONCUR '96, volume 1119 of LNCS, pages 179--194. Springer-Verlag, 1996. 20

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Uwe Nestmann and Benjamin C. Pierce. Decoding choice encodings. In Ugo Montanari and Vladimiro Sassone, editors, CONCUR '96: Concurrency Theory, 7th International Conference, volume 1119 of LNCS, pages 179--194, Pisa, Italy, August 1996. Springer-Verlag.

No context found.

U. Nestmann and B. C. Pierce. Decoding choice encodings. Journal of Information and Computation, 163:1--59, 2000.

No context found.

U. Nestmann and B.C. Pierce. Decoding choice encodings. In U. Montanari, editor, CONCUR 96, volume 1119 of Lecture Notes in Computer Science, pages 179--194. Springer-Verlag, 1996.

No context found.

Uwe Nestmann and Benjamin C. Pierce. Decoding choice encodings. In Proc. CONCUR'96, 1996.

No context found.

U. Nestmann and B. Pierce. Decoding choice encodings. In Proc. of CONCUR '96, volume 1119 of LNCS, pages 179--194. Springer-Verlag, 1996.

No context found.

U. Nestmann and B. Pierce. Decoding choice encodings. Journal of Information & Computation, 163:1--59, November 2000.

No context found.

Uwe Nestmann and Benjamin C. Pierce. Decoding choice encodings. In Proc. CONCUR'96, 1996.

No context found.

Uwe Nestmann and Benjamin C. Pierce. Decoding choice encodings. In Montanari and Sassone [MS96], pages 179-194. Revised full version as report ERCIM10 /97-R051, European Research Consortium for Informatics and Mathematics, 1997.

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