Results 1  10
of
48
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 ..."
Abstract

Cited by 97 (5 self)
 Add to MetaCart
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.
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 ..."
Abstract

Cited by 29 (9 self)
 Add to MetaCart
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.
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 ..."
Abstract

Cited by 21 (4 self)
 Add to MetaCart
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 ..."
Abstract

Cited by 18 (7 self)
 Add to MetaCart
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
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 ..."
Abstract

Cited by 17 (6 self)
 Add to MetaCart
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
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 ..."
Abstract

Cited by 13 (1 self)
 Add to MetaCart
) 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...
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 ..."
Abstract

Cited by 13 (3 self)
 Add to MetaCart
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
On the Expressive Power of Joint Input
 EXPRESS'98
, 1998
"... The joincalculus was introduced as an `extended subset' of the asynchronous πcalculus by amalgamating the three operators for input, restriction, and replication into a single operator, called definition, but with the additional capability to describe the atomic joint reception of values from two ..."
Abstract

Cited by 10 (0 self)
 Add to MetaCart
The joincalculus was introduced as an `extended subset' of the asynchronous πcalculus by amalgamating the three operators for input, restriction, and replication into a single operator, called definition, but with the additional capability to describe the atomic joint reception of values from two different channels. In this paper, we just extend the asynchronous πcalculus with joint input. By studying its expressive power, using slight variations of previously investigated choice encodings, we also conclude on the expressiveness of the joincalculus.
On the Generalized Dining Philosophers Problem
, 2001
"... We consider a generalization of the dining philosophers problem to arbitrary connection topologies. We focus on symmetric, fully distributed systems, and we address the problem of guaranteeing progress and lockoutfreedom, even in presence of adversary schedulers, by using randomized algorithms. We ..."
Abstract

Cited by 8 (2 self)
 Add to MetaCart
We consider a generalization of the dining philosophers problem to arbitrary connection topologies. We focus on symmetric, fully distributed systems, and we address the problem of guaranteeing progress and lockoutfreedom, even in presence of adversary schedulers, by using randomized algorithms. We show that the wellknown algorithms of Lehmann and Rabin do not work in the generalized case, and we propose an alternative algorithm based on the idea of letting the philosophers assign a random priority to their adjacent forks.
Reduction Semantics for Ambient Calculi
 Trans In) (Trans Cap) P ≻ (ν−→ p )〈M.P ′ 〉P ′′ P M −→CG (ν −→ p )(P ′ P ′′ ) (fn(M) ∩ −→ p = ∅) (Trans Amb) P
, 2004
"... First of all, I would like to thank my supervisor Dr. Iain C. C. Phillips, for his support and collaboration during this period of research. I thank Iain for having taught me to be more precise and sharp, and for long, detailed and inspiring discussions on the topic of this dissertation. Finally I t ..."
Abstract

Cited by 8 (5 self)
 Add to MetaCart
First of all, I would like to thank my supervisor Dr. Iain C. C. Phillips, for his support and collaboration during this period of research. I thank Iain for having taught me to be more precise and sharp, and for long, detailed and inspiring discussions on the topic of this dissertation. Finally I thank him for his enormous patience towards my stubbornness. I would like to thank Dr. Nobuko Yoshida for many useful discussions and for being very supportive and positive about my work. To Sergio Maffeis go thanks for many discussions on various subjects of research and philosophy during the last two years at Imperial College. He suggested an improvement to the solution for the leader election problem for the Ambient Calculus. I would like to thank also Andrew Phillips, and the concurrency group at Imperial for the Monday lunch meetings. This has been a wonderful forum for discussing various aspects of my work. I like to thank Prof. Chris Hankin and Dr. Sophia Drossopoulou for helping me on various occasions with administrative problems and (especially Chris) for supporting most of my travelling. I do not know how I could have ever achieved this without my husband, Steffen van Bakel. He