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Experiences with the PEPA performance modelling tools
 Proceedings of the Fourteenth UK Performance Engineering Workshop
, 1998
"... The PEPA language [1] is supported by a suite of modelling tools which assist in the solution and analysis of PEPA models. The design and development of these tools have been influenced by a variety of factors, including the wishes of other users of the tools to use the language for purposes which w ..."
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Cited by 35 (26 self)
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The PEPA language [1] is supported by a suite of modelling tools which assist in the solution and analysis of PEPA models. The design and development of these tools have been influenced by a variety of factors, including the wishes of other users of the tools to use the language for purposes which were not anticipated by the tool designers. In consequence, the suite of PEPA tools has adapted to attempt to serve the needs of these users while continuing to support the language designers themselves. In this paper we report on our use of the PEPA tools and give some advice gained from our experiences. 1
Exploiting Structure in Solution: Decomposing Composed Models
 Proceedings of 6th International Workshop on Process Algebra and Performance Modelling
, 1998
"... Since their introduction nearly ten years ago, compositionality has been reported as one of the major attractions of stochastic process algebras. The benefits that compositionality provides for model construction are readily apparent and have been demonstrated in numerous case studies. Early researc ..."
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Cited by 16 (3 self)
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Since their introduction nearly ten years ago, compositionality has been reported as one of the major attractions of stochastic process algebras. The benefits that compositionality provides for model construction are readily apparent and have been demonstrated in numerous case studies. Early research on the compositionality of the languages focussed on how the inherent structure could be used, in conjunction with equivalence relations, for model simplification and aggregation. In this paper we consider how far we have been able to take advantage of compositionality when it comes to solving the Markov process underlying a stochastic process algebra model and outline directions for future work in order for current results to be fully exploited. 1 Introduction Stochastic process algebras (SPA) were first proposed as a tool for performance and dependability modelling in 1989 [24]. At that time there was already a plethora of techniques for constructing performance models so the introducti...
Extending QuasiSeparability
 University of Bristol
, 1999
"... The advantages of compositionality and flexibility of stochastic process algebras has led to them being used to model increasingly larger and more complex systems. Models of such systems are inherently difficult to solve due principally to the size of their underlying state space. Therefore, tools w ..."
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Cited by 3 (2 self)
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The advantages of compositionality and flexibility of stochastic process algebras has led to them being used to model increasingly larger and more complex systems. Models of such systems are inherently difficult to solve due principally to the size of their underlying state space. Therefore, tools which support the evaluation of models expressed using stochastic process algebra must be able to utilise the full range of decomposition and solution techniques available. In this paper a class of models is considered which do not give rise to a product form solution but can nevertheless be decomposed into their components without loss of generality. The characterisation developed here generalises earlier published results, allowing a much wider range of models to be decomposed in this way. 1 Introduction In the study of stochastic process algebra we wish to consider not only how systems are to be specified, but also how complex systems can be simplified and solved efficiently. One part of ...
Approximating variance in nonproduct form decomposed models
 In Proc. of ICALP Workshops 2000 (PAPM
, 2000
"... A class of models is considered here which do not give rise to a product form solution but can nevertheless be decomposed into their components, subject to a property referred to as quasiseparability. Such a decomposition gives rise to expressions for marginal probabilities which may be used to der ..."
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Cited by 3 (1 self)
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A class of models is considered here which do not give rise to a product form solution but can nevertheless be decomposed into their components, subject to a property referred to as quasiseparability. Such a decomposition gives rise to expressions for marginal probabilities which may be used to derive potentially interesting system performance measures, such as the average state of the system. It is very important that some degree of confidence in such measures can also be given, however, we show here that it is not generally possible to calculate the variance exactly from the marginal probabilities. In this paper a simple approximation for the variance of the state a system of quasiseparable components is presented and evaluated. 1
Stochastic Process Algebras and their Application to Performance Modelling
 Proc. of TOOLSâ€™98 tutorials
, 1998
"... In this tutorial we present two major applications of process algebras to performance modelling. The first is the use of classical or timed process algebra to verify simulation models. The second is the direct use of stochastic process algebras to construct and solve performance models. The tutorial ..."
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In this tutorial we present two major applications of process algebras to performance modelling. The first is the use of classical or timed process algebra to verify simulation models. The second is the direct use of stochastic process algebras to construct and solve performance models. The tutorial presents an overview of the current trends and areas of active research, as well as their implications for performance engineering practice. 1 Introduction Process algebras emerged as a modelling technique for the functional analysis of concurrent systems approximately twenty years ago. Over the last decade there have been several attempts to take advantage of the attractive features of this modelling paradigm within the field of performance evaluation. The motivations for this work have been many but there have been just two fundamental approaches. Pooley pioneered the use of formally constructed process algebra models to verify simulation models, taking advantage of existing process alge...
Analysis of nonproduct form parallel queues using a Markovian process algebra
"... Abstract. In this paper we use the Markovian process algebra PEPA to specify and analyse a class of queueing models which, in general, do not give rise to a product form solution but can nevertheless be decomposed into their components to obtain a scalable solution. Such a decomposition gives rise t ..."
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Abstract. In this paper we use the Markovian process algebra PEPA to specify and analyse a class of queueing models which, in general, do not give rise to a product form solution but can nevertheless be decomposed into their components to obtain a scalable solution. Such a decomposition gives rise to expressions for marginal probabilities which may be used to derive potentially interesting system performance measures, such as the average number of jobs in the system. It is very important that some degree of confidence in such measures can also be given; however, we show here that it is not generally possible to calculate the variance exactly from the marginal probabilities. Hence, two approximations for the variance of the total population are presented and compared numerically. 1