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17
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 72 (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.
Compositional Performance Modelling with the TIPPtool
 PERFORMANCE EVALUATION
, 1998
"... Stochastic Process Algebras have been proposed as compositional specification formalisms for performance models. In this paper, we describe a tool which aims at realising all beneficial aspects of compositional performance modelling, the TIPPtool. It incorporates methods for compositional specificat ..."
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Cited by 53 (19 self)
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Stochastic Process Algebras have been proposed as compositional specification formalisms for performance models. In this paper, we describe a tool which aims at realising all beneficial aspects of compositional performance modelling, the TIPPtool. It incorporates methods for compositional specification as well as solution, based on stateofthearttechniques, and wrapped in a userfriendly graphical front end. Apart from highlighting the general benefits of the tool, we also discuss some lessons learned during development and application of the TIPPtool. A nontrivial model of a real life communication system serves as a case study to illustrate benefits and limitations.
Bisimulation Algorithms for Stochastic Process Algebras and their BDDbased Implementation
 In ARTS, LNCS 1601
, 1999
"... . Stochastic process algebras have been introduced in order to enable compositional performance analysis. The size of the state space is a limiting factor, especially if the system consists of many cooperating components. To fight state space explosion, various proposals for compositional aggregatio ..."
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Cited by 35 (13 self)
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. Stochastic process algebras have been introduced in order to enable compositional performance analysis. The size of the state space is a limiting factor, especially if the system consists of many cooperating components. To fight state space explosion, various proposals for compositional aggregation have been made. They rely on minimisation with respect to a congruence relation. This paper addresses the computational complexity of minimisation algorithms and explains how efficient, BDDbased data structures can be employed for this purpose. 1 Introduction Compositional application of stochastic process algebras (SPA) is particularly successful if the system structure can be exploited during Markov chain generation. For this purpose, congruence relations have been developed which justify minimisation of components without touching behavioural properties. Examples of such relations are strong equivalence [22], (strong and weak) Markovian bisimilarity [16] and extended Markovian bisimi...
Revisiting interactive Markov chains
 In Proc. Models for TimeCritical Systems
, 2002
"... 1 Introduction The advantages of using process algebras for the performance modeling and evaluation of concurrent systems due to their feature of compositionality have been widely recognized (see [12,2,18,9,5,3] and the references therein). Particularly simple and successful has been the extension o ..."
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Cited by 17 (1 self)
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1 Introduction The advantages of using process algebras for the performance modeling and evaluation of concurrent systems due to their feature of compositionality have been widely recognized (see [12,2,18,9,5,3] and the references therein). Particularly simple and successful has been the extension of standard process algebras with time delays whose duration follows an exponential probability distribution, called Markovian process algebras (see e.g. [12,2,18,9]). The &quot;timed &quot; behavior of systems specified with a Markovian process algebra can represented by a continuous time Markov chain (CTMC), i.e. a simple continuous time stochastic process where in each time point the future behavior of
Sigref  a symbolic bisimulation tool box
 IN ATVA, VOLUME 4218 OF LNCS
, 2006
"... We present a uniform signaturebased approach to compute the most popular bisimulations. Our approach is implemented symbolically using BDDs, which enables the handling of very large transition systems. Signatures for the bisimulations are built up from a few generic building blocks, which natura ..."
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Cited by 13 (5 self)
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We present a uniform signaturebased approach to compute the most popular bisimulations. Our approach is implemented symbolically using BDDs, which enables the handling of very large transition systems. Signatures for the bisimulations are built up from a few generic building blocks, which naturally correspond to efficient BDD operations. Thus, the definition of an appropriate signature is the key for a rapid development of algorithms for other types of bisimulation. We provide experimental evidence of the viability of this approach by presenting computational results for many bisimulations on realworld instances. The experiments show cases where our framework can handle state spaces efficiently that are far too large to handle for any tool that requires an explicit state space description. 1
Concurrency and Composition in a Stochastic World
, 2012
"... Abstract. We discuss conceptional and foundational aspects of Markov automata [22]. We place this model in the context of continuous and discretetime Markov chains, probabilistic automata and interactive Markov chains, and provide insight into the parallel execution of such models. We further give ..."
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Cited by 12 (3 self)
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Abstract. We discuss conceptional and foundational aspects of Markov automata [22]. We place this model in the context of continuous and discretetime Markov chains, probabilistic automata and interactive Markov chains, and provide insight into the parallel execution of such models. We further give a detailled account of the concept of relations on distributions, and discuss how this can generalise known notions of weak simulation and bisimulation, such as to fuse sequences of internal transitions. 1
A Complete Axiomatization for Observational Congruence of Prioritized FiniteState Behaviors
 in Proc. of the 27th Int. Colloquium on Automata, Languages and Programming (ICALP
, 2000
"... . Milner's complete proof system for observational congruence is crucially based on the possibility to equate divergent expressions to nondivergent ones by means of the axiom recX:(:X +E) = recX::E. In the presence of a notion of priority, where e.g. actions of type have a lower priority ..."
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Cited by 11 (4 self)
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. Milner's complete proof system for observational congruence is crucially based on the possibility to equate divergent expressions to nondivergent ones by means of the axiom recX:(:X +E) = recX::E. In the presence of a notion of priority, where e.g. actions of type have a lower priority than silent actions, this axiom is no longer sound because a action performable by E is preempted in the lefthand term but not in the righthand term. The problem of axiomatizing priority using the standard observational congruence has been open for a long time. Here we show that this can be done by introducing an auxiliary operator pri(E), by suitably modifying the axiom above and by introducing some new axioms. Our technique provides a complete axiomatization for Milner's observational congruence over nitestate terms of a process algebra with priority and recursion. 1 Introduction In the last years the expressiveness of classical process algebras has been extended in severa...
Towards Reliable Modelling with Stochastic Process Algebras
 Department of Computer Science, University of Bristol, Bristol
, 1999
"... Abstract In this thesis, we investigate reliable modelling within a stochastic process algebra framework. Primarily, we consider issues of variance in stochastic process algebras as a measure of model reliability. This is in contrast to previous research in the field which has tended to centre aroun ..."
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Abstract In this thesis, we investigate reliable modelling within a stochastic process algebra framework. Primarily, we consider issues of variance in stochastic process algebras as a measure of model reliability. This is in contrast to previous research in the field which has tended to centre around mean behaviour and steadystate solutions. We present a method of stochastic aggregation for analysing generallydistributed processes. This allows us more descriptive power in representing stochastic systems and thus gives us the ability to create more accurate models. We improve upon two welldeveloped Markovian process algebras and show how their simpler paradigm can be brought to bear on more realistic synchronisation models. Now, reliable performance figures can be obtained for systems, where previously only approximations of unknown accuracy were possible. Finally, we describe reliability definitions and variance metrics in stochastic models and demonstrate how systems can be made more reliable through careful combination under stochastic process algebra operators. ii Acknowledgements My three years in the department in Bristol have been a lot of fun and the person I have most to thank for this is my friend and mentor, Neil Davies. I should also acknowledge the funding from NATS for my project and especially the help of Suresh Tewari (NATS) and Gordon Hughes (SSRC).
Priority and Abstraction in Process Algebra
, 2007
"... More than 15 years ago, Cleaveland and Hennessy proposed an extension of the process algebra CCS in which some actions may take priority over others. The theory was equipped with a behavioral congruence based on strong bisimulation. This article gives a full account of the challenges in, and the sol ..."
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Cited by 2 (0 self)
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More than 15 years ago, Cleaveland and Hennessy proposed an extension of the process algebra CCS in which some actions may take priority over others. The theory was equipped with a behavioral congruence based on strong bisimulation. This article gives a full account of the challenges in, and the solutions employed for, defining a semantic theory of observation congruence for this process algebra. A full–abstraction result is presented whose proof relies on a novel approach based on successive approximations for identifying the largest congruence contained in an intuitive but naïve equivalence. Prioritized observation congruence is also characterized equationally for the class of finite processes, while its utility for system verification is demonstrated by an illustrative example.
Performance Evaluation := (Process Algebra + Model Checking) Markov Chains
 In Proc. CONCUR 2001
, 2001
"... Abstract. Markov chains are widely used in practice to determine system performance and reliability characteristics. The vast majority of applications considers continuoustime Markov chains (CTMCs). This tutorial paper shows how successful model specification and analysis techniques from concurren ..."
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Abstract. Markov chains are widely used in practice to determine system performance and reliability characteristics. The vast majority of applications considers continuoustime Markov chains (CTMCs). This tutorial paper shows how successful model specification and analysis techniques from concurrency theory can be applied to performance evaluation. The specification of CTMCs is supported by a stochastic process algebra, while the quantitative analysis of these models is tackled by means of model checking. Process algebra provides: (i) a highlevel specification formalism for describing CTMCs in a precise, modular and constraintoriented way, and (ii) means for the automated generation and aggregation of CTMCs. Temporal logic model checking provides: (i) a formalism to specify complex measuresofinterest in a lucid, compact and flexible way, (ii) automated means to quantify these measures over CTMCs, and (iii) automated measuredriven aggregation (lumping) of CTMCs. Combining process algebra and model checking constitutes a coherent framework for performance evaluation based on CTMCs. 1