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169
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 305 (36 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.”
The PEPA Workbench: A Tool to Support a Process Algebrabased Approach to Performance Modelling
 In Proceedings of the Seventh International Conference on Modelling Techniques and Tools for Computer Performance Evaluation, number 794 in Lecture Notes in Computer Science
, 1994
"... . In this paper we present a new technique for performance modelling and a tool supporting this approach. Performance Evaluation Process Algebra (PEPA) [1] is an algebraic language which can beused to build models of computer systems which capture information about the performance of the system. The ..."
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Cited by 174 (62 self)
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. In this paper we present a new technique for performance modelling and a tool supporting this approach. Performance Evaluation Process Algebra (PEPA) [1] is an algebraic language which can beused to build models of computer systems which capture information about the performance of the system. The PEPA language serves two purposes as a formal description language for computer system models. The performancerelated information in the model may be used to predict the performance of the system whereas the behavioural information in the model may be exploited when reasoning about the functional behaviour of the system (e.g. when finding deadlocks or when exhibiting equivalences between subcomponents). In this paper we concentrate on the performance aspects of the language. A method of reasoningaboutPEPA modelsproceedsby considering the derivation graph obtained from the model using the underlying operational semantics of the PEPA language. The derivation graph is systematically reduced ...
Multiprocessor and Distributed System Design: The Integration of Functional Specification and Performance Analysis Using Stochastic Process Algebras
, 1993
"... We introduce Stochastic Process Algebras as a novel approach for the structured design and analysis of both the functional behaviour and performance characteristics of parallel and distributed systems. This is achieved by integrating performance modelling and analysis into the powerful and well i ..."
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Cited by 139 (17 self)
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We introduce Stochastic Process Algebras as a novel approach for the structured design and analysis of both the functional behaviour and performance characteristics of parallel and distributed systems. This is achieved by integrating performance modelling and analysis into the powerful and well investigated formal description technique of process algebras. After advocating the use of stochastic process algebras as a modelling technique we recapitulate the foundations of classical process algebras. Then we present extensions of process algebras such that the requirements of performance analysis are taken into account. Examples illustrate the methodological advantages that are gained.
A tutorial on EMPA: A theory of concurrent processes with nondeterminism, priorities, probabilities and time
 Theoretical Computer Science
, 1998
"... In this tutorial we give an overview of the process algebra EMPA, a calculus devised in order to model and analyze features of realworld concurrent systems such as nondeterminism, priorities, probabilities and time, with a particular emphasis on performance evaluation. The purpose of this tutorial ..."
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Cited by 117 (11 self)
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In this tutorial we give an overview of the process algebra EMPA, a calculus devised in order to model and analyze features of realworld concurrent systems such as nondeterminism, priorities, probabilities and time, with a particular emphasis on performance evaluation. The purpose of this tutorial is to explain the design choices behind the development of EMPA and how the four features above interact, and to show that a reasonable trade off between the expressive power of the calculus and the complexity of its underlying theory has been achieved.
Liveness in Timed and Untimed Systems
, 1994
"... When proving the correctness of algorithms in distributed systems, one generally considers safety conditions and liveness conditions. The Input/Output (I/O) automaton model and its timed version have been used successfully, but have focused on safety conditions and on a restricted form of liveness c ..."
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Cited by 87 (17 self)
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When proving the correctness of algorithms in distributed systems, one generally considers safety conditions and liveness conditions. The Input/Output (I/O) automaton model and its timed version have been used successfully, but have focused on safety conditions and on a restricted form of liveness called fairness. In this paper we develop a new I/O automaton model, and a new timed I/O automaton model, that permit the verification of general liveness properties on the basis of existing verification techniques. Our models include a notion of environmentfreedom which generalizes the idea of receptiveness of other existing formalisms, and enables the use of compositional verification techniques.
Compiling RealTime Specifications into Extended Automata
 IEEE Transactions on Software Engineering
, 1992
"... We propose a method for the implementation and analysis of realtime systems, based on the compilation of specifications into extended automata. Such a method has been already adopted for the so called "synchronous" realtime programming languages. ..."
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Cited by 78 (8 self)
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We propose a method for the implementation and analysis of realtime systems, based on the compilation of specifications into extended automata. Such a method has been already adopted for the so called "synchronous" realtime programming languages.
A calculus for orchestration of web services.
 In Proc. of ESOP’07,
, 2007
"... Abstract Serviceoriented computing, an emerging paradigm for distributed computing based on the use of services, is calling for the development of tools and techniques to build safe and trustworthy systems, and to analyse their behaviour. Therefore, many researchers have proposed to use process ca ..."
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Cited by 75 (19 self)
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Abstract Serviceoriented computing, an emerging paradigm for distributed computing based on the use of services, is calling for the development of tools and techniques to build safe and trustworthy systems, and to analyse their behaviour. Therefore, many researchers have proposed to use process calculi, a cornerstone of current foundational research on specification and analysis of concurrent, reactive, and distributed systems. In this paper, we follow this approach and introduce C WS, a process calculus expressly designed for specifying and combining serviceoriented applications, while modelling their dynamic behaviour. We show that C WS can model all the phases of the life cycle of serviceoriented applications, such as publication, discovery, negotiation, orchestration, deployment, reconfiguration and execution. We illustrate the specification style that C WS supports by means of a large case study from the automotive domain and a number of more specific examples drawn from it.
Process Algebra for Performance Evaluation
, 2000
"... This paper surveys the theoretical developments in the field of stochastic process algebras, process algebras where action occurrences may be subject to a delay that is determined by a random variable. A huge class of resourcesharing systems  like largescale computers, clientserver architectur ..."
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Cited by 71 (13 self)
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This paper surveys the theoretical developments in the field of stochastic process algebras, process algebras where action occurrences may be subject to a delay that is determined by a random variable. A huge class of resourcesharing systems  like largescale computers, clientserver architectures, networks  can accurately be described using such stochastic specification formalisms.
Verification of an Audio Control Protocol
 FORMAL TECHNIQUES IN REALTIME AND FAULTTOLERANT SYSTEMS
, 1994
"... We analyze a simple version of a protocol developed by Philips for the physical layer of an interface bus that connects the various devices of some stereo equipment (tuner, CD player,...). The protocol, which uses Manchester encoding, has to deal with a significant uncertainty in the timing of event ..."
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Cited by 55 (7 self)
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We analyze a simple version of a protocol developed by Philips for the physical layer of an interface bus that connects the various devices of some stereo equipment (tuner, CD player,...). The protocol, which uses Manchester encoding, has to deal with a significant uncertainty in the timing of events, due to both hardware and software constraints. We present a formal specification of the protocol, and a proof of correctness for the case where the tolerance of the clocks used within the system is less than 1/17 . A counterexample shows that the protocol fails for tolerances greater than or equal to this value. The verification is carried out using a model of linear hybrid systems, which is similar to the phase transition system model of Manna and Pnueli, and the model of linear hybrid automata of Alur, Henzinger and Ho. The semantics of linear hybrid systems is defined via a translation to the timed I/O automata model of Lynch and Vaandrager.
Process Algebra for Discrete Event Simulation
 In Quantitative Methods in Parallel Systems
, 1993
"... We present a process algebra or programming language, based on CCS, which may be used to describe discrete event simulations with parallelism. It has extensions to describe the passing of time and probabilistic choice, either discrete, between a countable number of processes, or continuous to choose ..."
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Cited by 54 (3 self)
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We present a process algebra or programming language, based on CCS, which may be used to describe discrete event simulations with parallelism. It has extensions to describe the passing of time and probabilistic choice, either discrete, between a countable number of processes, or continuous to choose a random amount of time to wait. It has a clear operational semantics and we give approaches to denotational semantics given in terms of an algebra of equivalences over processes. It raises questions about when two simulations are equivalent and what we mean by nondeterminism in the context of the specification of a simulation. It also exemplifies some current approaches to adding time and probability to process algebras. 1 Introduction Imagine we wish to simulate the behaviour of a complex system with computerised components, such as a telephone network. First, let us look at the implementation of such a complex system. When it is implemented, typically work will start with some type of ...