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43
Relations in Concurrency
"... The theme of this paper is profunctors, and their centrality and ubiquity in understanding concurrent computation. Profunctors (a.k.a. distributors, or bimodules) are a generalisation of relations to categories. Here they are first presented and motivated via spans of event structures, and the seman ..."
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Cited by 263 (33 self)
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The theme of this paper is profunctors, and their centrality and ubiquity in understanding concurrent computation. Profunctors (a.k.a. distributors, or bimodules) are a generalisation of relations to categories. Here they are first presented and motivated via spans of event structures, and the semantics of nondeterministic dataflow. Profunctors are shown to play a key role in relating models for concurrency and to support an interpretation as higherorder processes (where input and output may be processes). Two recent directions of research are described. One is concerned with a language and computational interpretation for profunctors. This addresses the duality between input and output in profunctors. The other is to investigate general spans of event structures (the spans can be viewed as special profunctors) to give causal semantics to higherorder processes. For this it is useful to generalise event structures to allow events which “persist.”
NonInterleaving Semantics for Mobile Processes
 Theoretical Computer Science
, 1995
"... This paper studies causality in ßcalculus. Our notion of causality combines the dependencies given by the syntactic structure of processes with those originated by passing names. Our studies show that two transitions not causally related may however occur in a fixed ordering in any computation, i.e ..."
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Cited by 41 (19 self)
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This paper studies causality in ßcalculus. Our notion of causality combines the dependencies given by the syntactic structure of processes with those originated by passing names. Our studies show that two transitions not causally related may however occur in a fixed ordering in any computation, i.e., ßcalculus may implicitly express a precedence between actions. Our causality relation still induces the same partial order of transitions for all the computations that are obtained by shuffling transitions that are concurrent (i.e. related neither by causality nor by precedence). Other noninterleaving semantics are investigated and compared. The presentation takes advantage from a parametric definition of process behaviour given in an SOS style. All the results on bisimulationbased equivalences, congruences, axiomatizations and logics are taken (almost) without modifications from the interleaving theory. Finally, we extend our approach to higherorder ßcalculus, enriched with a spawn ...
The Integration Project for the JACK Environement
 BULLETIN OF THE EATCS
, 1994
"... JACK, standing for Just Another Concurrency Kit, is a new environment integrating a set of verification tools, supported by a graphical interface offering facilities to use these tools separately or in combination. The environment proposes several functionalities for the design, analysis and verif ..."
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Cited by 35 (12 self)
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JACK, standing for Just Another Concurrency Kit, is a new environment integrating a set of verification tools, supported by a graphical interface offering facilities to use these tools separately or in combination. The environment proposes several functionalities for the design, analysis and verification of concurrent systems specified using process algebra. Tools exchange information through a text format called Fc2. Users are able to graphically layout their specifications, that will be automatically converted into the Fc2 format and then minimised with respect to various kinds of equivalences. A branching time and action based logic, ACTL, is used to describe the properties that the specification must satisfy, and model checking of ACTL formulae on the specification is performed in linear time. A translator from Natural Language to ACTL formulae is provided, in order to simplify the job to describe the specification properties by ACTL formulae. A description of the graphical interface is given together with its functionalities and the exchange format used by the tools. As an example of use of JACK, we present a small case study within JACK, that covers both verification of a software system and verification of its properties.
Formal Characterisation of Immediate Actions in SPA with Nondeterministic Branching
 IN PROCEEDINGS OF THE 3RD WORKSHOP ON PROCESS ALGEBRA AND PERFORMANCE MODELLING
, 1995
"... ..."
Causality for Mobile Processes
 In Proceedings of ICALP'95, LNCS 944
, 1995
"... Abstract. We study causality in the ßcalculus. Our notion of causality combines the dependencies given by the syntactic structure of processes with those originated by passing names. It turns out that two transitions not causally related may although occur in a fixed ordering in any computation, i. ..."
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Cited by 29 (18 self)
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Abstract. We study causality in the ßcalculus. Our notion of causality combines the dependencies given by the syntactic structure of processes with those originated by passing names. It turns out that two transitions not causally related may although occur in a fixed ordering in any computation, i.e., ßcalculus may express implicitly a priority between actions. Our causality relation still induces the same partial order of transitions for all the computations that are obtained by shuffling transitions that are concurrent (= related neither by causality nor by priority). The presentation takes advantage from a parametric definition of process behaviour that highlights the essence of the topic. All the results on bisimulation based equivalences, congruences, axiomatizations and logics are taken (almost) for free from the interleaving theory. 1 Introduction The study of the behaviour of a distributed system may benefit from knowledge on the causal relation between its events. For examp...
A Logical Study of Distributed Transition Systems
, 1995
"... We extend labelled transition systems to distributed transition systems by labelling the transition relation with a finite set of actions, representing the fact that the actions occur as a concurrent step. We design an actionbased temporal logic in which one can explicitly talk about steps. The log ..."
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Cited by 29 (5 self)
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We extend labelled transition systems to distributed transition systems by labelling the transition relation with a finite set of actions, representing the fact that the actions occur as a concurrent step. We design an actionbased temporal logic in which one can explicitly talk about steps. The logic is studied to establish a variety of positive and negative results in terms of axiomatizability and decidability. Our positive results show that the step notion is amenable to logical treatment via standard techniques. They also help us to obtain a logical characterization of two well known models for distributed systems: labelled elementary net systems and labelled prime event structures. Our negative results show that demanding deterministic structures when dealing with a "noninterleaved " notion of transitions is, from a logical standpoint, very expressive. They also show that another well known model of distributed systems called asynchronous transition systems exhibits a surprising a...
Syntax, Semantics, Equivalences, and Axioms for MTIPP
 in Proc. of the 2nd Workshop on Process Algebras and Performance Modelling (PAPM '94
, 1994
"... The stochastic process algebra MTIPP has emerged from research in the field of process descriptions for random behaviour through time. This calculus has recently been shown to allow the calculation of performance measures (e.g. response times), purely functional statements (e.g. occurrences of deadl ..."
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Cited by 24 (1 self)
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The stochastic process algebra MTIPP has emerged from research in the field of process descriptions for random behaviour through time. This calculus has recently been shown to allow the calculation of performance measures (e.g. response times), purely functional statements (e.g. occurrences of deadlocks), as well as combined statements (e.g. optimal timeout values) [9, 11]. In contrast to classical process calculi each atomic action is supposed to happen after a delay that is characterised by a certain exponentially distributed random variable. In this report we present the language together with its operational semantics, that defines Markovian labelled transition systems as a combination of classical actionoriented transition systems and Markovian processes, especially continuous time Markov chains. In order to reflect different behavioural aspects we define a hierarchy of bisimulation equivalences and show that two of them are congruences. Finally we present equational laws for our...
Relaxed memory models: an operational approach
, 2009
"... Memory models define an interface between programs written in some language and their implementation, determining which behaviour the memory (and thus a program) is allowed to have in a given model. A minimal guarantee memory models should provide to the programmer is that wellsynchronized, that is ..."
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Cited by 20 (1 self)
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Memory models define an interface between programs written in some language and their implementation, determining which behaviour the memory (and thus a program) is allowed to have in a given model. A minimal guarantee memory models should provide to the programmer is that wellsynchronized, that is, datarace free code has a standard semantics. Traditionally, memory models are defined axiomatically, setting constraints on the order in which memory operations are allowed to occur, and the programming language semantics is implicit as determining some of these constraints. In this work we propose a new approach to formalizing a memory model in which the model itself is part of a weak operational semantics for a (possibly concurrent) programming language. We formalize in this way a model that allows write operations to the store to be buffered. This enables us to derive the ordering constraints from the weak semantics of programs, and to prove, at the programming language level, that the weak semantics implements the usual interleaving semantics for datarace free programs, hence in particular that it implements the usual semantics for sequential code.
A Process Algebra with Distributed Priorities
 Theoretical Computer Science
, 1996
"... . This paper presents a process algebra for distributed systems in which some actions may take precedence over others. In contrast with existing approaches to priorities, our algebra only allows actions to preempt others at the same #location" and therefore captures a notion of localizedprecedence. ..."
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Cited by 14 (3 self)
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. This paper presents a process algebra for distributed systems in which some actions may take precedence over others. In contrast with existing approaches to priorities, our algebra only allows actions to preempt others at the same #location" and therefore captures a notion of localizedprecedence. Using Park's and Milner's notion of strong bisimulation as a basis, we develop a behavioral congruence and axiomatize it for #nite processes; we also derive an associated observational congruence. Simple examples highlight the utility of the theory. 1 Introduction Process algebras #11, 13# provide widely studied frameworks for modeling and verifying concurrent systems #9#. Such theories typically consist of a simple language with a wellde#ned operational semantics given in terms of labeled transition systems; a behavioral equivalence is then used to relate implementations and speci#cations, which are both given as terms in the language. In order to facilitate compositional reasoning, in wh...