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21
A Comparison of Performance Evaluation Process Algebra and Generalized Stochastic Petri Nets
 In Proc. 6th International Workshop on Petri Nets and Performance Models
, 1995
"... Generalized Stochastic Petri Nets (GSPN)and Performance Evaluation Process Algebra (PEPA) can both be used to study qualitative and quantitative behaviour of systems in a single environment. This paper presents a comparison of the two formalisms in terms of the facilities that they provide to the mo ..."
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Cited by 32 (8 self)
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Generalized Stochastic Petri Nets (GSPN)and Performance Evaluation Process Algebra (PEPA) can both be used to study qualitative and quantitative behaviour of systems in a single environment. This paper presents a comparison of the two formalisms in terms of the facilities that they provide to the modeller, considering both the definition and the analysis of the performance model. Our goal is to provide a better understanding of both formalisms, and to prepare a fertile ground for exchanging ideas and techniques between the two. To illustrate similarities and differences, we make the different issues more concrete by means of an example modelling resource contention. 1 Introduction In this paper we present a comparison of two formalisms which may be used to develop performance models as continuous time Markov chains (CTMC). Generalized stochastic Petri nets (GSPN) is a wellestablished high level modelling paradigm which has been widely applied in performance analysis. In contrast, Per...
A Throughput Approximation Algorithm for Decision Free Processes
 Proc. of 6th Process Algebra and Performance Modelling Workshop
, 1996
"... We present a characterization of a class of processes that correspond to 1safe Marked Graphs. The main property of this type of models is that there is no choice allowed in the model. In the Petri net domain this means that places have only one input and one output unweighted arc. Conditions are pr ..."
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Cited by 9 (3 self)
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We present a characterization of a class of processes that correspond to 1safe Marked Graphs. The main property of this type of models is that there is no choice allowed in the model. In the Petri net domain this means that places have only one input and one output unweighted arc. Conditions are presented, under which a process term corresponds to a Marked Graph. We refer to such models as decision free processes. Their throughput is approximated with an efficient aggregation algorithm in a divide and conquer fashion. The reduction factor of the state space size is usually more than one order of magnitude while the deviation of the exact results remains in the range of 5%. Transformation techniques in the style of highlevel equational laws are presented that allow in some cases to modify parts of the model so that the application of this aggregation technique becomes possible. 1 Introduction In the stochastic process algebra (SPA) modelling paradigm systems are described as an inte...
Throughput Approximation of Decision Free Processes Using Decomposition
 In Proc. of the 7th Int. Workshop on Petri Nets and Performance Models
, 1997
"... We present an approach for the efficient approximation of the throughput of decision free processes, a class of stochastic process algebra models. Stochastic process algebras are modeling formalisms which are based on communicating sequential processes, in contrast to stochastic Petri nets which foc ..."
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Cited by 8 (5 self)
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We present an approach for the efficient approximation of the throughput of decision free processes, a class of stochastic process algebra models. Stochastic process algebras are modeling formalisms which are based on communicating sequential processes, in contrast to stochastic Petri nets which focus on causality and concurrency. The algorithm we are using is based on model decomposition at the specification level of stochastic process algebras and has been adopted from marked graphs, a well known subclass of Petri nets. It works in a divide and conquer fashion and it is able to reduce the size of the state space by more than one order of magnitudewhile the deviation of the exact result is relatively low. 1 Introduction The exact performance analysis of discrete event dynamic systems (DEDS) is computationally expensive and for complex models often impossible. Approximation methods are helpful in getting insight into the performance of such systems when other methods fail. One class ...
Threads and processes
 In Programming Ruby: The Pragmatic Programmer’s Guide
, 2001
"... reliable software performance modelling using ..."
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Stochastic Process Algebras  Between LOTOS and Markov Chains
 Comp. Netw. and ISDN Syst
, 1997
"... This paper introduces stochastic process algebras as an approach for the structured design and analysis of both the functional behavior and performance characteristics of parallel and distributed systems. This is achieved by integrating stochastic modelling and analysis into process algebras like CC ..."
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Cited by 6 (2 self)
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This paper introduces stochastic process algebras as an approach for the structured design and analysis of both the functional behavior and performance characteristics of parallel and distributed systems. This is achieved by integrating stochastic modelling and analysis into process algebras like CCS or LOTOS. We demonstrate how notions of equivalent behavior  substantial for process algebras  stand in a new light for stochastic process algebras. In particular we discuss the impact of stochastic versions of such equivalences on compositional performance analysis by means of a running example. In addition we discuss analysis techniques, tool support and include a survey of related work as well as recent trends in this area. Keywords: Process Algebra, Performance Analysis, Stochastic Time, Markov Chains, Bisimulation. 1 Introduction  Distributed Systems and their Formal Description One may safely assume that almost all substantial future computer and information systems will be ...
A new proposal for the synchronization in sPBC
 In Proc. Third IEEE Int. Conference on Application of Concurrent to System Design (ACSD’03
, 2002
"... In this paper we present a new proposal for the synchronization of a stochastic extension of nite Petri Box Calculus, sPBC, in which multiactions have a stochastic delay associated, which is taken from a negative exponential distribution. We de ne for the language both an operational and a deno ..."
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In this paper we present a new proposal for the synchronization of a stochastic extension of nite Petri Box Calculus, sPBC, in which multiactions have a stochastic delay associated, which is taken from a negative exponential distribution. We de ne for the language both an operational and a denotational semantics, using a class of labelled stochastic Petri net as supporting values.
Using Stochastic Petri Nets to Predict Quality of Service Attributes of ComponentBased Software Architectures
"... The Quality of Service attributes of a software component heavily depend on its environment. For example, if a component uses a highly unreliable service, its own reliability is likely to decrease as well. This relation can be described with parametric contracts, which model the dependence between p ..."
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The Quality of Service attributes of a software component heavily depend on its environment. For example, if a component uses a highly unreliable service, its own reliability is likely to decrease as well. This relation can be described with parametric contracts, which model the dependence between provided and required services of a component. Until now, parametric contracts can only model singlethreaded systems. We plan to extend parametric contracts with Stochastic Petri nets to model multithreaded systems. This enables the detection of resource conflicts and the consideration of the influence of concurrency on Quality of Service attributes, like performance. 1
PerformanceOriented Refinement
, 2001
"... We introduce the probabilistic action system formalism which combines refinement with performance. Performance is expressed by means of probability and expected costs. Probability is needed to express uncertainty present in physical environments. Expected costs express physical or abstract quantitie ..."
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Cited by 1 (1 self)
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We introduce the probabilistic action system formalism which combines refinement with performance. Performance is expressed by means of probability and expected costs. Probability is needed to express uncertainty present in physical environments. Expected costs express physical or abstract quantities that describe a system. They encode the performance objective. The behaviour of probabilistic action systems is described by traces of expected costs. Corresponding notions of refinement and simulationbased proof rules are introduced. Formal notations like B [2] or action systems [8] support a notion of refinement. Refinement relates an abstract specification A to a more deterministic concrete specification C. Knowing A and C one proves C refines, or implements, specification A. In this study we consider specification A as given and concern ourselves with a way to find a good candidate for specification according to their performance. The performance of a
CONTINUOUS APPROXIMATION OF PEPA MODELS AND PETRI NETS
"... server semantics Modelling very large systems that consist of many similar components can lead to state space explosion. Continuous approximation can avoid this. In the stochastic process algebra PEPA, models with large numbers of identical components can be approximated in a continuous fashion by a ..."
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server semantics Modelling very large systems that consist of many similar components can lead to state space explosion. Continuous approximation can avoid this. In the stochastic process algebra PEPA, models with large numbers of identical components can be approximated in a continuous fashion by a set of coupled ordinary differential equations (ODEs). Similarly, timed continuous Petri nets can be used to approximate behaviour via ODEs where there are many servers. These two approaches are compared and infinite and finite server semantics are considered.
Expressing Performance Requirements usingRegular Expressions to Specify Stochastic Probes over
"... ABSTRACT This paper describes how soft performance bounds can be expressed for software systems using stochastic probes over stochastic process algebra models. These stochastic probes are specified using a regular expression syntax that describes the behaviour that must be observed in a model before ..."
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ABSTRACT This paper describes how soft performance bounds can be expressed for software systems using stochastic probes over stochastic process algebra models. These stochastic probes are specified using a regular expression syntax that describes the behaviour that must be observed in a model before a performance measurement can be started or stopped. We demonstrate the use of stochastic probes on a 661; 960 state parallel, redundant web server model to verify its passagetime performance characteristics.