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29
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 97 (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.
Deriving Bisimulation Congruences in the DPO Approach to Graph Rewriting
, 2004
"... Motivated by recent work on the derivation of labelled transitions and bisimulation congruences from unlabelled reaction rules, we show how to solve this problem in the DPO (doublepushout) approach to graph rewriting. Unlike in previous approaches, we consider graphs as objects, instead of arrows, ..."
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Cited by 61 (10 self)
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Motivated by recent work on the derivation of labelled transitions and bisimulation congruences from unlabelled reaction rules, we show how to solve this problem in the DPO (doublepushout) approach to graph rewriting. Unlike in previous approaches, we consider graphs as objects, instead of arrows, of the category under consideration. This allows us to present a very simple way of deriving labelled transitions (called rewriting steps with borrowed context) which smoothly integrates with the DPO approach, has a very constructive nature and requires only a minimum of category theory. The core part of this paper is the proof sketch that the bisimilarity based on rewriting with borrowed contexts is a congruence relation.
A Theory of Bisimulation for the picalculus
, 1993
"... We study a new formulation of bisimulation for the calculus [MPW92], which we have called open bisimulation ( ). In contrast with the previously known bisimilarity equivalences, is preserved by all calculus operators, including input prefix. The differences among all these equivalences alread ..."
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Cited by 39 (0 self)
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We study a new formulation of bisimulation for the calculus [MPW92], which we have called open bisimulation ( ). In contrast with the previously known bisimilarity equivalences, is preserved by all calculus operators, including input prefix. The differences among all these equivalences already appear in the sublanguage without name restrictions: Here the definition of can be factorised into a "standard" part which, modulo the different syntax of actions, is the CCS bisimulation, and a part specific to the calculus, which requires name instantiation. Attractive features of are: a simple axiomatisation (of the finite terms), with a completeness proof which leads to the construction of minimal canonical representatives for the equivalence classes of ; an "efficient" characterisation, based on a modified transition system. This characterisation seems promising for the development of automatedverification tools and also shows the callbyneed flavour of . Although in the...
Saturated semantics for reactive systems
 LOGIC IN COMPUTER SCIENCE
, 2006
"... The semantics of process calculi has traditionally been specified by labelled transition systems (LTS), but with the development of name calculi it turned out that reaction rules (i.e., unlabelled transition rules) are often more natural. This leads to the question of how behavioural equivalences (b ..."
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Cited by 27 (15 self)
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The semantics of process calculi has traditionally been specified by labelled transition systems (LTS), but with the development of name calculi it turned out that reaction rules (i.e., unlabelled transition rules) are often more natural. This leads to the question of how behavioural equivalences (bisimilarity, trace equivalence, etc.) defined for LTS can be transferred to unlabelled transition systems. Recently, in order to answer this question, several proposals have been made with the aim of automatically deriving an LTS from reaction rules in such a way that the resulting equivalences are congruences. Furthermore these equivalences should agree with the intended semantics, whenever one exists. In this paper we propose saturated semantics, based on a weaker notion of observation and orthogonal to all the previous proposals, and we demonstrate the appropriateness of our semantics by means of two examples: logic programming and a subset of the open πcalculus. Indeed, we prove that our equivalences are congruences and that they coincide with logical equivalence and open bisimilarity respectively, while equivalences studied in previous works are strictly finer.
Semantic Barbs and Biorthogonality
"... Abstract. We use the framework of biorthogonality to introduce a novel semantic definition of the concept of barb (basic observable) for process calculi. We develop a uniform basic theory of barbs and demonstrate its robustness by showing that it gives rise to the correct observables in specific pro ..."
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Cited by 17 (1 self)
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Abstract. We use the framework of biorthogonality to introduce a novel semantic definition of the concept of barb (basic observable) for process calculi. We develop a uniform basic theory of barbs and demonstrate its robustness by showing that it gives rise to the correct observables in specific process calculi which model synchronous, asynchronous and broadcast communication regimes. 1
Bisimulation by unification
 Proc. AMAST 2002, LNCS 2422
, 2002
"... Abstract. We propose a methodology for the analysis of open systems based on process calculi and bisimilarity. Open systems are seen as coordinators (i.e. terms with placeholders), that evolve when suitable components (i.e. closed terms) fill in their placeholders. The distinguishing feature of ou ..."
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Cited by 13 (7 self)
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Abstract. We propose a methodology for the analysis of open systems based on process calculi and bisimilarity. Open systems are seen as coordinators (i.e. terms with placeholders), that evolve when suitable components (i.e. closed terms) fill in their placeholders. The distinguishing feature of our approach is the definition of a symbolic operational semantics for coordinators that exploits spatial/modal formulae as labels of transitions and avoids the universal closure of coordinators w.r.t. all components. Two kinds of bisimilarities are then defined, called strict and large, which differ in the way formulae are compared. Strict bisimilarity implies large bisimilarity which, in turn, implies the one based on universal closure. Moreover, for process calculi in suitable formats, we show how the symbolic semantics can be defined constructively, using unification. Our approach is illustrated on a toy process calculus with ccslike communication within ambients. 1
Abstract Semantics by Observable Contexts
, 2008
"... The operational behavior of interactive systems is usually given in terms of transition systems labeled with actions, which, when visible, represent both observations and interactions with the external world. The abstract semantics is given in terms of behavioral equivalences, which depend on the ac ..."
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Cited by 9 (2 self)
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The operational behavior of interactive systems is usually given in terms of transition systems labeled with actions, which, when visible, represent both observations and interactions with the external world. The abstract semantics is given in terms of behavioral equivalences, which depend on the action labels and on the amount of branching structure considered. Behavioural equivalences are often congruences with respect to the operations of the language, and this property expresses the compositionality of the abstract semantics. A simpler approach, inspired by classical formalisms like λcalculus, Petri nets, term and graph rewriting, and pioneered by the Chemical Abstract Machine [1], defines operational semantics by means of structural axioms and reaction rules. Process calculi representing complex systems, in particular those able to generate and communicate names, are often defined in this way, since structural axioms give a clear idea of the intended structure of the states while reaction rules, which are often nonconditional, give a direct account of the possible steps. Transitions caused by reaction rules, however, are not labeled, since
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 ..."
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Cited by 8 (5 self)
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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
An Interactive Semantics of Logic Programming
 THEORY AND PRACTICE OF LOGIC PROGRAMMING
, 2001
"... We apply to logic programming some recently emerging ideas from the field of reductionbased communicating systems, with the aim of giving evidence of the hidden interactions and the coordination mechanisms that rule the operational machinery of such a programming paradigm. The semantic framework we ..."
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Cited by 8 (6 self)
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We apply to logic programming some recently emerging ideas from the field of reductionbased communicating systems, with the aim of giving evidence of the hidden interactions and the coordination mechanisms that rule the operational machinery of such a programming paradigm. The semantic framework we have chosen for presenting our results is tile logic, which has the advantage of allowing a uniform treatment of goals and observations and of applying abstract categorical tools for proving the results. As main contributions, we mention the finitary presentation of abstract unification, and a concurrent and coordinated abstract semantics consistent with the most common semantics of logic programming. Moreover, the compositionality of the tile semantics is guaranteed by standard results, as it reduces to check that the tile systems associated to logic programs enjoy the tile decomposition property. An extension of the approach for handling constraint systems is also discussed.