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A brief history of process algebra
 Theor. Comput. Sci
, 2004
"... Abstract. This note addresses the history of process algebra as an area of research in concurrency theory, the theory of parallel and distributed systems in computer science. Origins are traced back to the early seventies of the twentieth century, and developments since that time are sketched. The a ..."
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Cited by 57 (1 self)
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Abstract. This note addresses the history of process algebra as an area of research in concurrency theory, the theory of parallel and distributed systems in computer science. Origins are traced back to the early seventies of the twentieth century, and developments since that time are sketched. The author gives his personal views on these matters. He also considers the present situation, and states some challenges for the future.
Implementation of Symbolic Model Checking for Probabilistic Systems
, 2002
"... In this thesis, we present ecient implementation techniques for probabilistic model checking, a method which can be used to analyse probabilistic systems such as randomised distributed algorithms, faulttolerant processes and communication networks. A probabilistic model checker inputs a probabilist ..."
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Cited by 52 (19 self)
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In this thesis, we present ecient implementation techniques for probabilistic model checking, a method which can be used to analyse probabilistic systems such as randomised distributed algorithms, faulttolerant processes and communication networks. A probabilistic model checker inputs a probabilistic model and a speci cation, such as \the message will be delivered with probability 1", \the probability of shutdown occurring is at most 0.02" or \the probability of a leader being elected within 5 rounds is at least 0.98", and can automatically verify if the speci cation is true in the model.
Refinementoriented probability for CSP
, 1995
"... Jones and Plotkin give a general construction for forming a probabilistic powerdomain over any directedcomplete partial order [Jon90, JP89]. We apply their technique to the failures/divergences semantic model for Communicating Sequential Processes [Hoa85]. The resulting probabilistic model supports ..."
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Cited by 35 (5 self)
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Jones and Plotkin give a general construction for forming a probabilistic powerdomain over any directedcomplete partial order [Jon90, JP89]. We apply their technique to the failures/divergences semantic model for Communicating Sequential Processes [Hoa85]. The resulting probabilistic model supports a new binary operator, probabilistic choice, and retains all operators of CSP including its two existing forms of choice. An advantage of using the general construction is that it is easy to see which CSP identities remain true in the probabilistic model. A surprising consequence however is that probabilistic choice distributes through all other operators; such algebraic mobility means that the syntactic position of the choice operator gives little information about when the choice actually must occur. That in turn leads to some interesting interaction between probability and nondeterminism. A simple communications protocol is used to illustrate the probabilistic algebra, and several sugg...
Nondeterminism and Probabilistic Choice: Obeying the Laws
 In Proc. 11th CONCUR, volume 1877 of LNCS
, 2000
"... In this paper we describe how to build semantic models that support both nondeterministic choice and probabilistic choice. Several models exist that support both of these constructs, but none that we know of satisfies all the laws one would like. Using domaintheoretic techniques, we show how models ..."
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Cited by 25 (2 self)
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In this paper we describe how to build semantic models that support both nondeterministic choice and probabilistic choice. Several models exist that support both of these constructs, but none that we know of satisfies all the laws one would like. Using domaintheoretic techniques, we show how models can be devised using the "standard model" for probabilistic choice, and then applying modified domaintheoretic models for nondeterministic choice. These models are distinguished by the fact that the expected laws for nondeterministic choice and probabilistic choice remain valid. We also describe some potential applications of our model to aspects of security.
Model Checking of RealTime Systems: A Telecommunications Application
 IN PROCEEDINGS OF THE 19TH INTERNATIONAL CONFERENCE ON SOFTWARE ENGINEERING
, 1997
"... We describe the application of model checking tools to analyze a realtime software challenge in the design of Lucent Technologies' 5ESS telephone switching system. We use two tools: COSPAN for checking realtime properties, and TPWB for checking probabilistic specifications. We report on the feedba ..."
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Cited by 18 (1 self)
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We describe the application of model checking tools to analyze a realtime software challenge in the design of Lucent Technologies' 5ESS telephone switching system. We use two tools: COSPAN for checking realtime properties, and TPWB for checking probabilistic specifications. We report on the feedback given by the tools, and based on our experience, discuss the advantages and the limitations of the approach used.
Analysing randomized distributed algorithms
 Validation of Stochastic Systems
, 2004
"... Abstract. Randomization is of paramount importance in practical applications and randomized algorithms are used widely, for example in coordinating distributed computer networks, message routing and cache management. The appeal of randomized algorithms is their simplicity and elegance. However, thi ..."
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Cited by 9 (1 self)
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Abstract. Randomization is of paramount importance in practical applications and randomized algorithms are used widely, for example in coordinating distributed computer networks, message routing and cache management. The appeal of randomized algorithms is their simplicity and elegance. However, this comes at a cost: the analysis of such systems become very complex, particularly in the context of distributed computation. This arises through the interplay between probability and nondeterminism. To prove a randomized distributed algorithm correct one usually involves two levels: classical, assertionbased reasoning, and a probabilistic analysis based on a suitable probability space on computations. In this paper we describe a number of approaches which allows us to verify the correctness of randomized distributed algorithms. 1
Towards automated proof support for probabilistic distributed systems
 In Proceedings of Logic for Programming and Automated Reasoning, volume 3835 of LNAI
, 2005
"... Abstract. The mechanisation of proofs for probabilistic systems is particularly challenging due to the verification of realvalued properties that probability entails: experience indicates [12, 4, 11] that there are many difficulties in automating realnumber arithmetic in the context of other progr ..."
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Cited by 8 (5 self)
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Abstract. The mechanisation of proofs for probabilistic systems is particularly challenging due to the verification of realvalued properties that probability entails: experience indicates [12, 4, 11] that there are many difficulties in automating realnumber arithmetic in the context of other program features. In this paper we propose a framework for verification of probabilistic distributed systems based on the generalisation of Kleene algebra with tests that has been used as a basis for development of concurrency control in standard programming [7]. We show that verification of realvalued properties in these systems can be considerably simplified, and moreover that there is an interpretation which is susceptible to counterexample search via state exploration, despite the underlying realnumber domain. 1
Metric semantics for reactive probabilistic processes
, 1997
"... In this thesis we present three mathematical frameworks for the modelling of reactive probabilistic communicating processes. We first introduce generalised labelled transition systems as a model of such processes and introduce an equivalence, coarser than probabilistic bisimulation, over these syst ..."
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Cited by 6 (1 self)
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In this thesis we present three mathematical frameworks for the modelling of reactive probabilistic communicating processes. We first introduce generalised labelled transition systems as a model of such processes and introduce an equivalence, coarser than probabilistic bisimulation, over these systems. Two processes are identified with respect to this equivalence if, for all experiments, the probabilities of the respective processes passing a given experiment are equal. We next consider a probabilistic process calculus including external choice, internal choice, actionguarded probabilistic choice, synchronous parallel and recursion. We give operational semantics for this calculus be means of our generalised labelled transition systems and show that our equivalence is a congruence for this language. Following the methodology introduced by de Bakker & Zucker, we then give denotational semantics to the calculus by means of a complete metric space of probabilistic processes. The derived metric, although not an ultrametric, satisfies the intuitive property that the distance between two processes tends to 0 if a measure of the dif
Y.R.: Model checking prioritized timed automata
 ATVA 2005. LNCS
, 2005
"... Abstract. Priorities are often used to resolve conflicts in timed systems. However, priorities are not directly supported by stateofart model checkers. Often, a designer has to either abstract the priorities leading to a high degree of nondeterminism or model the priorities using existing primitiv ..."
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Cited by 4 (3 self)
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Abstract. Priorities are often used to resolve conflicts in timed systems. However, priorities are not directly supported by stateofart model checkers. Often, a designer has to either abstract the priorities leading to a high degree of nondeterminism or model the priorities using existing primitives. In this work, it is shown how prioritized timed automata can make modelling prioritized timed systems easier through the support for priority specification and model checking. The verification of prioritized timed automata requires a subtraction operation to be performed on two clock zones, represented by DBMs, for which we propose an algorithm to generate the minimal number of zones partitioned. After the application of a series of DBM subtraction operations, the number of zones generated become large. We thus propose an algorithm to reduce the final number of zones partitioned by merging some of them. A typical bus arbitration example is used to illustrate the benefits of the proposed algorithms. Due to the support for prioritization and zone reduction, we observe that there is a 50 % reduction in the number of modes and 44 % reduction in the number of transitions.
Design and Verification of Distributed Recovery Blocks with CSP
, 1998
"... A case study on the application of Communicating Sequential Processes (CSP) to the design and veri cation of faulttolerant realtime systems is presented. The distributed recovery block (DRB) scheme is a design technique for the uniform treatment of hardware and software faults in realtime systems ..."
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Cited by 1 (1 self)
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A case study on the application of Communicating Sequential Processes (CSP) to the design and veri cation of faulttolerant realtime systems is presented. The distributed recovery block (DRB) scheme is a design technique for the uniform treatment of hardware and software faults in realtime systems. Through a simple faulttolerant realtime system design using the DRB scheme, the case study illustrates a paradigm for specifying faulttolerant software and demonstrates how the different behavioural aspects of a faulttolerant realtime system design can be separately and systematically specified, formulated, and verified using an integrated set of formal techniques based on CSP.