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39
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 95 (9 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.
Weak Bisimulation for Fully Probabilistic Processes
, 1999
"... Bisimulations that abstract from internal computation have proven to be useful for verification of compositionally defined transition systems. In the literature of probabilistic extensions of such transition systems, similar bisimulations are rare. In this paper, we introduce weak and branching bisi ..."
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Cited by 57 (7 self)
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Bisimulations that abstract from internal computation have proven to be useful for verification of compositionally defined transition systems. In the literature of probabilistic extensions of such transition systems, similar bisimulations are rare. In this paper, we introduce weak and branching bisimulation for fully probabilistic systems, transition systems where nondeterministic branching is replaced by probabilistic branching. In contrast to the nondeterministic case, both relations coincide. We give an algorithm to decide weak (and branching) bisimulation with a time complexity cubic in the number of states of the fully probabilistic system. This meets the worst case complexity for deciding branching bisimulation in the nondeterministic case. In addition, the relation is shown to be a congruence with respect to the operators of PLSCCS , a lazy synchronous probabilistic variant of CCS. We illustrate that due to these properties, weak bisimulation provides all the crucial ingredients...
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 52 (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.
A Formal Approach to the Integration of Performance Aspects in the Modeling and Analysis of Concurrent Systems
 Information and Computation
, 1998
"... A formal approach for modeling and analyzing concurrent systems is proposed which integrates performance characteristics in the early stages of the design process. The approach relies on both stochastically timed process algebras and stochastically timed Petri nets in order to exploit their compleme ..."
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Cited by 25 (10 self)
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A formal approach for modeling and analyzing concurrent systems is proposed which integrates performance characteristics in the early stages of the design process. The approach relies on both stochastically timed process algebras and stochastically timed Petri nets in order to exploit their complementary advantages. The approach is instantiated to the case of EMPA (Extended Markovian Process Algebra), introduced together with the collection of its four semantics and the notion of equivalence that are required in order to implement the approach. Finally, the case study of the alternating bit protocol is presented to illustrate the adequacy of the approach. 1
Towards Performance Evaluation with General Distributions in Process Algebras
 in Proc. of the 9th Int. Conf. on Concurrency Theory (CONCUR '98), LNCS 1466:405422
, 1998
"... . We present a process algebra for the performance modeling and evaluation of concurrent systems whose activity durations are expressed through general probability distributions. We first determine the class of generalized semiMarkov processes (GSMPs) as being the class of stochastic processes on w ..."
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Cited by 23 (9 self)
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. We present a process algebra for the performance modeling and evaluation of concurrent systems whose activity durations are expressed through general probability distributions. We first determine the class of generalized semiMarkov processes (GSMPs) as being the class of stochastic processes on which we must rely for performance evaluation to be possible. Then we argue that in this context the right semantics for algebraic terms is a variant of the ST semantics which accounts for both functional and performance aspects. The GSMP based process algebra we propose is introduced together with its formal semantics, an example of performance evaluation, and a notion of probabilistic bisimulation based equivalence accounting for action durations which is shown to be a congruence. 1 Introduction The aim of this paper is to develop a core calculus suitable for the performance evaluation of concurrent systems whose activity durations are expressed through general probability distributions. I...
Algebra and Logic for Resourcebased Systems Modelling
 UNDER CONSIDERATION FOR PUBLICATION IN MATH. STRUCT. IN COMP. SCIENCE
, 2009
"... ... often, models are required to be executable, as a simulation, on a computer. In this paper, we present some contributions to the processtheoretic and logical foundations of discreteevent modelling with resources and processes. We present a process calculus with an explicit representation of re ..."
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Cited by 17 (10 self)
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... often, models are required to be executable, as a simulation, on a computer. In this paper, we present some contributions to the processtheoretic and logical foundations of discreteevent modelling with resources and processes. We present a process calculus with an explicit representation of resources in which processes and resources coevolve. The calculus is closely connected to a logic that may be used as a specification language for properties of models. The logic is strong enough to allow requirements that a system has certain structure; for example, that it is a parallel composite of subsystems. This work consolidates, extends, and improves upon aspects of earlier work of ours in this area. An extended example, consisting of a semantics for a simple parallel programming language, indicates a connection with separating logics for concurrency.
Semantics for Structured Systems Modelling and Simulation
"... Simulation modelling is an important tool for exploring and reasoning about complex systems. Many supporting languages are available. Commonly occurring features of these languages are constructs capturing concepts such as process, resource, and location. We describe a mathematical framework that su ..."
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Cited by 16 (12 self)
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Simulation modelling is an important tool for exploring and reasoning about complex systems. Many supporting languages are available. Commonly occurring features of these languages are constructs capturing concepts such as process, resource, and location. We describe a mathematical framework that supports a modelling idiom based on these core concepts, and which adopts stochastic methods for representing the environments within which systems exist. We explain how this framework can be used to give a semantics to a simulation modelling language, Core Gnosis, that includes basic constructs for process, resource, and location. We include a brief discussion of a logic for reasoning about models that is compositional with respect to their structure. Our mathematical analysis of systems in terms of process, resource, location, and stochastic environment, together with a language that captures these concepts quite directly, yields an efficient and robust modelling framework within which natural mathematical reasoning about systems is captured.
Denotational Semantics for ProcessBased Simulation Languages. Part I: piDemos
, 1997
"... In this paper we present a method for translating the synchronisation behaviour of a process oriented discrete event simulation language into a process algebra. Such translations serve two purposes. The first exploits the formal structure of the target process algebraic representations to provide pr ..."
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Cited by 15 (10 self)
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In this paper we present a method for translating the synchronisation behaviour of a process oriented discrete event simulation language into a process algebra. Such translations serve two purposes. The first exploits the formal structure of the target process algebraic representations to provide proofs of properties of the source system (such as deadlock freedom, fairness, liveness, ...) which can be very difficult to establish by simulation experiment. The second exploits the denotational semantics to better understand the language constructs as abstract entities and to reason about simulation models. Here we give the intuition and present the basic mechanisms using the ßDemos simulation language and the CCS and SCCS process algebras. The analysis of the synchronisations of full Demos is treated in a companion paper.
A calculus and logic of resources and processes
 FAC, 18:495 – 517
, 2006
"... Recent advances in logics for reasoning about resources provide a new approach to compositional reasoning in interacting systems. We present a calculus of resources and processes, based on a development of Milner's synchronous calculus of communication systems, SCCS, that uses an explicit model of ..."
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Cited by 15 (7 self)
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Recent advances in logics for reasoning about resources provide a new approach to compositional reasoning in interacting systems. We present a calculus of resources and processes, based on a development of Milner's synchronous calculus of communication systems, SCCS, that uses an explicit model of resource. Our calculus models the coevolution of resources and processes with synchronization constrained by the availability of resources. We provide a logical characterization, analogous to HennessyMilner logic's characterization of bisimulation in CCS, of bisimulation between resource processes which is compositional in the concurrent and local structure of systems.