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Implementation of a Compositional Performance Analysis Algorithm for Probabilistic I/O Automata
 IN PROCEEDINGS OF 1999 WORKSHOP ON PROCESS ALGEBRA AND PERFORMANCE MODELING (PAPM99). PRENSAS UNIVERSITARIAS DE
, 1999
"... In previous papers, we defined the probabilistic I/O automata model for specification and modeling of probabilistic concurrent systems, and we showed how certain performance measures for such systems could be computed compositionally, one component at a time, without the need for explicit constr ..."
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Cited by 11 (5 self)
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In previous papers, we defined the probabilistic I/O automata model for specification and modeling of probabilistic concurrent systems, and we showed how certain performance measures for such systems could be computed compositionally, one component at a time, without the need for explicit construction of the full global state space. In this paper, we report on our experiences in constructing and testing a computer implemention of these compositional analysis algorithms. Our implementation, which is coded in the functional programming language Standard ML, uses exact rational arithmetic to calculate performance measures, and it is also capable of producing symbolic rational function expressions that describe the dependence of performance measures on a system parameter.
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).
A Construction and Analysis Tool Based on the Stochastic Process Algebra TIPP
 In Proceedings, TACAS Workshop, volume 1055 of Lecture Notes in Computer Science
, 1996
"... 1 There are many ways to incorporate a notion of time into process algebras in order to integrate functional design and performance analysis. One major research strand, stochastic process algebras, concentrates on the annotation of actions with exponentially distributed random variables. This paper ..."
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Cited by 10 (1 self)
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1 There are many ways to incorporate a notion of time into process algebras in order to integrate functional design and performance analysis. One major research strand, stochastic process algebras, concentrates on the annotation of actions with exponentially distributed random variables. This paper presents a tool for the functional analysis and performance evaluation of complex systems based on the stochastic process algebra paradigm. The TIPPtool provides facilities for model specification, reachability analysis, as well as several numerical algorithms for the solution of the underlying Markov chain and the computation of performance measures. 1 Introduction Stochastic process algebras (SPA) have been introduced as an extension of classical process algebras, like CCS or CSP, with timing information aiming mainly at the integration of functional design and quantitative analysis of computer systems. Time is represented by attaching random variables to every activity in the model, de...
Towards a superset of Basic Lotos for Performance Prediction
 Proc. of 6th Process Algebra and Performance Modelling Workshop
, 1996
"... Stochastic process algebras (SPA) provide primitive operators that serve as means to incorporate stochastic timing aspects into a process algebraic specification. In this paper we add some comfortable operators to an SPA where the passing of time is separated from the occurrence of activities. We pr ..."
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Cited by 9 (3 self)
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Stochastic process algebras (SPA) provide primitive operators that serve as means to incorporate stochastic timing aspects into a process algebraic specification. In this paper we add some comfortable operators to an SPA where the passing of time is separated from the occurrence of activities. We present a superset of Basic Lotos which integrates probabilistic branching and exponentially distributed time delays into the language, as well as value passing. The treatment of these ingredients is formally defined on the (interleaving) semantic model. After explaining the details of the language`s semantics, we define a congruence relation based on Milner`s observational congruence that is central for the reduction of the semantic model into a Continuous Time Markov Chain. 1 Introduction Stochastic Process Algebras have emerged from the desire to allow performance analysis of specifications based on process algebras. For this purpose, randomly distributed time delays are associated with ea...
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 ...
An Operator for Symmetry Representation and Exploitation in Stochastic Process Algebras
 Twente (The Netherlands
, 1997
"... Stochastic process algebras have been introduced to enable compositional performance analysis. State space explosion is a frequently observed problem, especially if the system consists of many cooperating components. This paper introduces symmetric parallel composition, an operator to specify a set ..."
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Stochastic process algebras have been introduced to enable compositional performance analysis. State space explosion is a frequently observed problem, especially if the system consists of many cooperating components. This paper introduces symmetric parallel composition, an operator to specify a set of identical components that are cooperating in parallel. Its operational semantics is consistent with usual parallel composition whereas the state space explosion problem is drastically reduced. We highlight this fact by means of a comparative case study. 1 Introduction Compositional application of stochastic process algebra (SPA) is particularly successful, if the system under consideration is given by a large number of identical components. In this case, equivalences (congruences) can be used to exploit symmetries in order to reduce the state space underlying the model. First, however, the symmetries have to be detected by either applying the semantic rules or by introducing some kind of...
Technique and tool for symbolic representation and manipulation of stochastic transition systems
 TR IMMD 7 2/98, Universitat ErlangenNurnberg
, 1998
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Stochastic Process Algebras  Constructive Specification Techniques Integrating Functional, Performance and Dependability Aspects
 Quantitative Methods in Parallel Systems
, 1995
"... Q uantitative M odeling I n P arallel S ystems ..."
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A Compact File Format for Labeled Transition Systems
, 2001
"... A compact open file format for labeled transition systems, which are commonly used in specification and verification of concurrent systems, is introduced. This combination of openness, both in specification and implementation, and compactness is unprecedented, since existing formats in this field ..."
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Cited by 4 (1 self)
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A compact open file format for labeled transition systems, which are commonly used in specification and verification of concurrent systems, is introduced. This combination of openness, both in specification and implementation, and compactness is unprecedented, since existing formats in this field are either not compact, yielding files too large to be easily handled, or proprietary, hampering the development of e#cient tools.
Stochastic Process Algebras
"... Abstract. In this tutorial we give an introduction to stochastic process algebras and their use in performance modelling, with a focus on the PEPA formalism. A brief introduction is given to the motivations for extending classical process algebra with stochastic times and probabilistic choice. We th ..."
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Abstract. In this tutorial we give an introduction to stochastic process algebras and their use in performance modelling, with a focus on the PEPA formalism. A brief introduction is given to the motivations for extending classical process algebra with stochastic times and probabilistic choice. We then present an introduction to the modelling capabilities of the formalism and the tools available to support Markovian based analysis. The chapter is illustrated throughout by small examples, demonstrating the use of the formalism and the tools. 1