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30
A Calculus of Broadcasting Systems
 SCIENCE OF COMPUTER PROGRAMMING
, 1991
"... CBS is a simple and natural CCSlike calculus where processes speak one at a time and are heard instantaneously by all others. Speech is autonomous, contention between speakers being resolved nondeterministically, but hearing only happens when someone else speaks. Observationally meaningful laws dif ..."
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Cited by 61 (8 self)
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CBS is a simple and natural CCSlike calculus where processes speak one at a time and are heard instantaneously by all others. Speech is autonomous, contention between speakers being resolved nondeterministically, but hearing only happens when someone else speaks. Observationally meaningful laws differ from those of CCS. The change from handshake communication in CCS to broadcast in CBS permits several advances. (1) Priority, which attaches only to autonomous actions, is simply added to CBS in contrast to CCS, where such actions are the result of communication. (2) A CBS simulator runs a process by returning a list of values it broadcasts. This permits a powerful combination, CBS with the host language. It yields several elegant algorithms. Only processes with a unique response to each input are needed in practice, so weak bisimulation is a congruence. (3) CBS subsystems are interfaced by translators; by mapping messages to silence, these can restrict hearing and hide speech. Reversi...
Fair Simulation
 Information and Computation
, 1997
"... The simulation preorder for labeled transition systems is defined locally as a game that relates states with their immediate successor states. Simulation enjoys many appealing properties. First, simulation has a fully abstract semantics: system S simulates system I iff every computation tree embedd ..."
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Cited by 49 (18 self)
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The simulation preorder for labeled transition systems is defined locally as a game that relates states with their immediate successor states. Simulation enjoys many appealing properties. First, simulation has a fully abstract semantics: system S simulates system I iff every computation tree embedded in the unrolling of I can be embedded also in the unrolling of S. Second, simulation has a logical characterization: S simulates I iff every universal branchingtime formula satisfied by S is satisfied also by I. It follows that simulation is a suitable notion of implementation, and it is the coarsest abstraction of a system that preserves universal branchingtime properties. Third, based on its local definition, simulation between finitestate systems can be checked in polynomial time. Finally, simulation implies tracecontainment, which cannot be defined locally and requires polynomial space for verification. Hence simulation is widely used both in manual and in automatic verification. ...
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 44 (2 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 ...
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...
On the Complexity of Verifying Concurrent Transition Systems
, 2000
"... In implementation verification, we check that an implementation is correct with respect to a specification by checking whether the behaviors of a transition system that models the program's implementation correlate with the behaviors of a transition system that models its specification. In this p ..."
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Cited by 30 (6 self)
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In implementation verification, we check that an implementation is correct with respect to a specification by checking whether the behaviors of a transition system that models the program's implementation correlate with the behaviors of a transition system that models its specification. In this paper, we investigate the effect of concurrency on the complexity of implementation verification. We consider tracebased and treebased approaches to the verification of concurrent transition systems, with and without fairness. Our results show that in almost all cases the complexity of the problem is exponentially harder than that of the sequential case. Thus, as in the modelchecking verification methodology, the stateexplosion problem cannot be avoided. A preliminary version of this work appeared in the proceedings of the 8th Conference on Concurrency Theory. y Department of Applied Mathematics & Computer Science, Weizmann institute, Rehovot 76100, Israel. Email: harel@wisdom.weizm...
Supervisory Control of Nondeterministic Systems with Driven Events via Prioritized Synchronization and Trajectory Models
 SIAM Journal of Control and Optimization
, 1995
"... We study the supervisory control of nondeterministic discrete event dynamical systems (DEDS's) with driven events in the setting of prioritized synchronization and trajectory models introduced by Heymann. Prioritized synchronization captures the notions of controllable, uncontrollable, and driven e ..."
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Cited by 25 (7 self)
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We study the supervisory control of nondeterministic discrete event dynamical systems (DEDS's) with driven events in the setting of prioritized synchronization and trajectory models introduced by Heymann. Prioritized synchronization captures the notions of controllable, uncontrollable, and driven events in a natural way, and we use it for constructing supervisory controllers. The trajectory model is used for characterizing the behavior of nondeterministic DEDS's since it is a sufficiently detailed model (in contrast to the less detailed language or failures models), and serves as a language congruence with respect to the operation of prioritized synchronization. We obtain results concerning controllability and observability in this general setting. Keywords: discrete event systems, supervisory control, nondeterministic automata, driven events, prioritized synchronization, trajectory models AMS (MOS) subject classifications: 68Q75, 93B25, 93C83 1 Introduction Supervisory control o...
Modal Logic, Transition Systems and Processes
, 1994
"... Transition systems can be viewed either as process diagrams or as Kripke structures. The first perspective is that of process theory, the second that of modal logic. This paper shows how various formalisms of modal logic can be brought to bear on processes. Notions of bisimulation can not only be mo ..."
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Cited by 24 (3 self)
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Transition systems can be viewed either as process diagrams or as Kripke structures. The first perspective is that of process theory, the second that of modal logic. This paper shows how various formalisms of modal logic can be brought to bear on processes. Notions of bisimulation can not only be motivated by operations on transition systems, but they can also be suggested by investigations of modal formalisms. To show that the equational view of processes from process algebra is closely related to modal logic, we consider various ways of looking at the relation between the calculus of basic process algebra and propositional dynamic logic. More concretely, the paper contains preservation results for various bisimulation notions, a result on the expressive power of propositional dynamic logic, and a definition of bisimulation which is the proper notion of invariance for concurrent propositional dynamic logic. Keywords: modal logic, transition systems, bisimulation, process algebra 1 In...
Verification of Fair Transition Systems
, 1998
"... . In program verification, we check that an implementation meets its specification. Both the specification and the implementation describe the possible behaviors of the program, though at different levels of abstraction. We distinguish between two approaches to implementation of specifications. The ..."
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Cited by 19 (9 self)
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. In program verification, we check that an implementation meets its specification. Both the specification and the implementation describe the possible behaviors of the program, though at different levels of abstraction. We distinguish between two approaches to implementation of specifications. The first approach is tracebased implementation, where we require every computation of the implementation to correlate to some computation of the specification. The second approach is treebased implementation, where we require every computation tree embodied in the implementation to correlate to some computation tree embodied in the specification. The two approaches to implementation are strongly related to the lineartime versus branchingtime dichotomy in temporal logic. In this work we examine the tracebased and the treebased approachesfrom a complexitytheoretic point of view. We consider and compare the complexity of verification of fair transition systems, modeling both the implement...
Representing Nondeterministic and Probabilistic Behaviour in Reactive Processes
, 1993
"... . In this paper we investigate ways of modelling communicating processes that display both nondeterministic and probabilistic behaviour. We present an operational model for a probabilistic version of CSP, and describe a number of ways of abstracting a denotational semantics from such a model, so as ..."
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Cited by 18 (0 self)
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. In this paper we investigate ways of modelling communicating processes that display both nondeterministic and probabilistic behaviour. We present an operational model for a probabilistic version of CSP, and describe a number of ways of abstracting a denotational semantics from such a model, so as to represent a process by a set of probability functions, one function for each way of resolving the nondeterministic choices. We then prove an interesting although disappointingresult, which shows that no such denotational model can be compositional. We end by identifying a problem with the operational model, which is shared by all similar models known to us, and briefly give some indications as to how this problem might be overcome. 1. Introduction In recent years, an important problem in the study of communicating systems has been the modelling of probabilistic behaviour. This is necessary if we are to argue formally about unreliable behaviour (for example that displayed by an unre...
On the Axiomatizability of Ready Traces, Ready Simulation and Failure Traces
"... We provide an answer to an open question, posed by van Glabbeek [4], regarding the axiomatizability of ready trace semantics. We prove that ..."
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Cited by 17 (12 self)
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We provide an answer to an open question, posed by van Glabbeek [4], regarding the axiomatizability of ready trace semantics. We prove that