Results 1  10
of
61
The Möbius Framework and Its Implementation
"... The Möbius framework is an environment for supporting multiple modeling formalisms and solution techniques. Models expressed in formalisms that are compatible with the framework are translated into equivalent models using Mobius framework components. This translation preserves the structure of the m ..."
Abstract

Cited by 113 (21 self)
 Add to MetaCart
(Show Context)
The Möbius framework is an environment for supporting multiple modeling formalisms and solution techniques. Models expressed in formalisms that are compatible with the framework are translated into equivalent models using Mobius framework components. This translation preserves the structure of the models, allowing e#cient solutions. The framework is implemented in the tool by a welldefined abstract functional interface. Models and solution techniques interact with one another through the use of the standard interface, allowing them to interact with Mobius framework components, not formalism components. This permits novel combinations of modeling techniques, and will be a catalyst for new research in modeling techniques. This paper describes our approach, focusing on the "atomic model." We describe the formal description of the Mobius components as well as their implementations in our software tool.
Modelbased evaluation: From dependability to security
 IEEE TRANSACTIONS ON DEPENDABLE AND SECURE COMPUTING
, 2004
"... The development of techniques for quantitative, modelbased evaluation of computer system dependability has a long and rich history. A wide array of modelbased evaluation techniques are now available, ranging from combinatorial methods, which are useful for quick, roughcut analyses, to statebased ..."
Abstract

Cited by 99 (5 self)
 Add to MetaCart
The development of techniques for quantitative, modelbased evaluation of computer system dependability has a long and rich history. A wide array of modelbased evaluation techniques are now available, ranging from combinatorial methods, which are useful for quick, roughcut analyses, to statebased methods, such as Markov reward models, and detailed, discreteevent simulation. The use of quantitative techniques for security evaluation is much less common, and has typically taken the form of formal analysis of small parts of an overall design, or experimental red teambased approaches. Alone, neither of these approaches is fully satisfactory, and we argue that there is much to be gained through the development of a sound modelbased methodology for quantifying the security one can expect from a particular design. In this work, we survey existing modelbased techniques for evaluating system dependability, and summarize how they are now being extended to evaluate system security. We find that many techniques from dependability evaluation can be applied in the security domain, but that significant challenges remain, largely due to fundamental differences between the accidental nature of the faults commonly assumed in dependability evaluation, and the intentional, human nature of cyber attacks.
PEPA nets: A structured performance modelling formalism
 Performance Evaluation
, 2003
"... In this paper we describe a formalism which uses the stochastic process algebra PEPA as the inscription language for labelled stochastic Petri nets. Viewed in another way, the net is used to provide a structure for linking related PEPA systems. The combined modelling language naturally represents su ..."
Abstract

Cited by 41 (23 self)
 Add to MetaCart
(Show Context)
In this paper we describe a formalism which uses the stochastic process algebra PEPA as the inscription language for labelled stochastic Petri nets. Viewed in another way, the net is used to provide a structure for linking related PEPA systems. The combined modelling language naturally represents such applications as mobile code systems where the PEPA terms are used to model the program code which moves between network hosts (the places in the net). We describe the implementation of a tool to support this modelling formalism and apply this to model a hierarchical cellular network. 1
A fluid analysis framework for a Markovian process algebra
, 2010
"... Markovian process algebras, such as PEPA and stochastic πcalculus, bring a powerful compositional approach to the performance modelling of complex systems. However, the models generated by process algebras, as with other interleaving formalisms, are susceptible to the state space explosion problem. ..."
Abstract

Cited by 41 (27 self)
 Add to MetaCart
Markovian process algebras, such as PEPA and stochastic πcalculus, bring a powerful compositional approach to the performance modelling of complex systems. However, the models generated by process algebras, as with other interleaving formalisms, are susceptible to the state space explosion problem. Models with only a modest number of process algebra terms can easily generate so many states that they are all but intractable to traditional solution techniques. Previous work aimed at addressing this problem has presented a fluidflow approximation allowing the analysis of systems which would otherwise be inaccessible. To achieve this, systems of ordinary differential equations describing the fluid flow of the stochastic process algebra model are generated informally. In this paper, we show formally that for a large class of models, this fluidflow analysis can be directly derived from the stochastic process algebra model as an approximation to the mean number of component types within the model. The nature of the fluid approximation is derived and characterised by direct comparison with the Chapman–Kolmogorov equations underlying the Markov model. Furthermore, we compare the fluid approximation with the exact solution using stochastic simulation and we are able to demonstrate that it is a very accurate approximation in many cases. For the first time, we also show how to extend these techniques naturally to generate systems of differential equations approximating higher order moments of model component counts. These are important performance characteristics for estimating, for instance, the variance of the component counts. This is very necessary if we are to understand how precise the fluidflow calculation is, in a given modelling situation.
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 ..."
Abstract

Cited by 37 (29 self)
 Add to MetaCart
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
Implementing a Stochastic Process Algebra within the Möbius Modeling Framework
 PROCEEDINGS OF THE FIRST JOINT PAPMPROBMIV WORKSHOP
, 2001
"... Many formalisms and solution methods exist for performance and dependability modeling. However, different formalisms have different advantages and strengths, and no one formalism is universally used. The Möbius ..."
Abstract

Cited by 26 (3 self)
 Add to MetaCart
Many formalisms and solution methods exist for performance and dependability modeling. However, different formalisms have different advantages and strengths, and no one formalism is universally used. The Möbius
Scalable Differential Analysis of Process Algebra Models
"... The exact performance analysis of largescale software systems with discretestate approaches is difficult because of the wellknown problem of statespace explosion. This paper considers this problem with regard to the stochastic process algebra PEPA, presenting a deterministic approximation to the ..."
Abstract

Cited by 24 (8 self)
 Add to MetaCart
(Show Context)
The exact performance analysis of largescale software systems with discretestate approaches is difficult because of the wellknown problem of statespace explosion. This paper considers this problem with regard to the stochastic process algebra PEPA, presenting a deterministic approximation to the underlying Markov chain model based on ordinary differential equations. The accuracy of the approximation is assessed by means of a substantial case study of a distributed multithreaded application.
Analysing distributed Internet worm attacks using continuous statespace approximation of process algebra models
 JOURNAL OF COMPUTER AND SYSTEM SCIENCES 74 (2008) 1013–1032
, 2008
"... ..."
Automatic Extraction of PEPA Performance Models from UML Activity Diagrams Annotated with the MARTE Profile
"... Recent trends in software engineering lean towards modelcentric development methodologies, a context in which the UML plays a crucial role. To provide modellers with quantitative insights into their artifacts, the UML benefits from a framework for software performance evaluation provided by MARTE, t ..."
Abstract

Cited by 18 (3 self)
 Add to MetaCart
(Show Context)
Recent trends in software engineering lean towards modelcentric development methodologies, a context in which the UML plays a crucial role. To provide modellers with quantitative insights into their artifacts, the UML benefits from a framework for software performance evaluation provided by MARTE, the UML profile for modeldriven development of Real Time and Embedded Systems. MARTE offers a rich semantics which is general enough to allow different quantitative analysis techniques to act as underlying performance engines. In the present paper we explore the use of the stochastic process algebra PEPA as one such engine, providing a procedure to systematically map activity diagrams onto PEPA models. Independent activity flows are translated into sequential automata which coordinate at the synchronisation points expressed by fork and join nodes of the activity. The PEPA performance model is interpreted against a Markovian semantics which allows the calculation of performance indices such as throughput and utilisation. We also discuss the implementation of a new software tool powered by the popular Eclipse platform which implements the fully automatic translation from MARTEannotated UML activity diagrams to PEPA models.
The Möbius StateLevel Abstract Functional Interface
 In Proc. of the 12th Int. Conf. on Modelling Techniques and Tools for Computer Performance Evaluation (TOOLS 2002
, 2003
"... A key advantage of the Möbius modeling environment is the ease with which one can incorporate new modeling formalisms, model composition and connection methods, and model solution methods. We present a new statelevel abstract functional interface (AFI) for Möbius that allows numerical solution meth ..."
Abstract

Cited by 15 (9 self)
 Add to MetaCart
(Show Context)
A key advantage of the Möbius modeling environment is the ease with which one can incorporate new modeling formalisms, model composition and connection methods, and model solution methods. We present a new statelevel abstract functional interface (AFI) for Möbius that allows numerical solution methods to communicate with Möbius statelevel models via the abstraction of a labeled transition system. This abstraction and its corresponding implementation yield an important separation of concerns: It is possible to treat separately the problem of representing large labeled transition systems, like generator matrices of continuoustime Markov chains, and the problem of analyzing these systems. For example, any numerical solver (e.g., Jacobi, SOR, or uniformization) that accesses a model through the Möbius statelevel AFI can operate on a variety of statespace representations, including "onthefly," diskbased, sparsematrix, Kronecker, and matrixdiagram representations, without requiring that the solver implementation be changed to match the statespace representation. This abstraction thus avoids redundant implementations of solvers and stategeneration techniques, eases research cooperation, and simplifies comparisons of approaches as well as benchmarking. In addition to providing a formal definition of the Möbius statelevel AFI, we illustrate its use on two statespace representations (a sparse matrix and a Kronecker representation) and on several numerical s...