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A Stochastic CausalityBased Process Algebra
, 1995
"... This paper discusses stochastic extensions of a simple process algebra in a causalitybased setting. Atomic actions are supposed to happen after a delay that is determined by a stochastic variable with a certain distribution. A simple stochastic type of event structures is discussed, restricting the ..."
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Cited by 34 (12 self)
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This paper discusses stochastic extensions of a simple process algebra in a causalitybased setting. Atomic actions are supposed to happen after a delay that is determined by a stochastic variable with a certain distribution. A simple stochastic type of event structures is discussed, restricting the distribution functions to be exponential. A corresponding operational semantics of this model is given and compared to existing (interleaved) approaches. Secondly, a stochastic variant of event structures is discussed where distributions are of a much more general nature, viz. of phasetype. This includes exponential, Erlang, Coxian and mixtures of exponential distributions. 1. INTRODUCTION
Probabilistic resource failure in realtime process algebra
 IN PROCEEDINGS CONCUR 98
, 1998
"... ..."
Testing Semantics for Probabilistic LOTOS
, 1995
"... In this paper we present a probabilistic extension of LOTOS which is upward compatible with LOTOS. We present testing semantics for the reactive and generative models described in [vGSST90]. While there is a certain lose of the meaning of probabilities in the reactive model, testing with probabilist ..."
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Cited by 11 (7 self)
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In this paper we present a probabilistic extension of LOTOS which is upward compatible with LOTOS. We present testing semantics for the reactive and generative models described in [vGSST90]. While there is a certain lose of the meaning of probabilities in the reactive model, testing with probabilistic tests proves to be too strong, because it does not relate behavior expressions which we expect to be equivalent. This is why we introduce the limited generative model, where tests are not allowed to have explicit probabilities. We give a fully abstract characterization for the reactive model, while we give alternative characterizations (based on a set of essential tests) for the generative and limited generative models. We also present some algebraic laws for each of the models, including some laws which establish the difference between the three models.
Performance Analysis and True Concurrency Semantics
 In T. Rus and C. Rattray, eds, Theories and Experiences for RealTime System Development
, 1994
"... This paper addresses the subject of linking functional specifications to performance analysis in a process algebraic context. It presents a timed, probabilistic extension of a process algebraic formalism and its application to performance analysis. More specifically, an extension of a subset of LOTO ..."
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Cited by 9 (5 self)
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This paper addresses the subject of linking functional specifications to performance analysis in a process algebraic context. It presents a timed, probabilistic extension of a process algebraic formalism and its application to performance analysis. More specifically, an extension of a subset of LOTOS is presented equipped with a truly concurrent semantical model based on bundle event structures. It is investigated how semiMarkov chains can be obtained from functional specifications using this semantical model. The use of a true concurrency model enables us to distinguish between nondeterminism and parallelism, to reduce the state explosion problem and, moreover, to analyse part of the system without considering other (irrelevant) parts. An example illustrates the proposed approach. 1 Introduction The study of formal methods for the specification, design, and analysis of distributed systems has been an important research topic over the past decade. Initially, the research in this ar...
On Specifying RealTime Systems in a CausalityBased Setting
, 1996
"... . Event structures are a prominent noninterleaving model for concurrency. Realtime event structures associate a set of time instants to events, modelling absolute time constraints, and to causal dependencies, modelling relative delays between causally dependent events. We introduce this novel tempo ..."
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Cited by 9 (4 self)
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. Event structures are a prominent noninterleaving model for concurrency. Realtime event structures associate a set of time instants to events, modelling absolute time constraints, and to causal dependencies, modelling relative delays between causally dependent events. We introduce this novel temporal model and show how it can be used to provide a denotational semantics to a realtime variant of a process algebra akin to LOTOS. This formalism includes a timedaction prefix which constrains the occurrence time of actions, a timeout and watchdog (i.e., timed interrupt) operator. An eventbased operational semantics for this formalism is presented that is shown to be consistent with the denotational semantics. As an example we use an infinite buffer with time constraints on the message latency and the rates of accepting and producing data. 1 Introduction Timed extensions of interleaving models for concurrency have been investigated thoroughly in the last decade. Although there are many...
Partial Order Models for Quantitative Extensions of LOTOS
, 1997
"... Event structures are a prominent model for noninterleaving concurrency. The use of event structures for providing a compositional noninterleaving semantics to LOTOS without data is studied. In particular, several quantitative extensions of event structures are proposed that incorporate notions lik ..."
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Cited by 3 (1 self)
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Event structures are a prominent model for noninterleaving concurrency. The use of event structures for providing a compositional noninterleaving semantics to LOTOS without data is studied. In particular, several quantitative extensions of event structures are proposed that incorporate notions like timeboth of deterministic and stochastic natureand probability. The suitability of these models for giving a noninterleaving semantics to a timed, stochastic and probabilistic extension of LOTOS is investigated. Consistency between the event structure semantics and an (eventbased) operational semantics is addressed for the different quantitative variants of LOTOS and is worked out for the timed case in more detail. These consistency results facilitate the coherent use of an interleaving and a noninterleaving semantic view in a single design trajectory and provide a justification for the event structure semantics. As a running example an infinite buffer is used in which gradually t...
Hiding Resources that Can Fail: An Axiomatic Perspective
, 2001
"... In earlier work, we presented a process algebra, PACSR, that uses a notion of resource failure to capture probabilistic behavior in reactive systems. PACSR also supports an operator for resource hiding. In this paper, we carefully consider the interaction between these two features from an axiomatic ..."
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Cited by 1 (0 self)
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In earlier work, we presented a process algebra, PACSR, that uses a notion of resource failure to capture probabilistic behavior in reactive systems. PACSR also supports an operator for resource hiding. In this paper, we carefully consider the interaction between these two features from an axiomatic perspective. For this purpose, we introduce a subset of PACSR, called "PACSRlite," that allows us to isolate the semantic issues surrounding resource hiding in a probabilistic setting, and provide a sound and complete axiomatization of strong bisimulation for this fragment.
A True Concurrency Semantics for ETLOTOS
, 1997
"... One of the central objectives of the LOTOS restandardisation activity is to define an enhanced LOTOS language which supports realtime specification. The timed extension is based upon a timed LOTOS proposal ETLOTOS. This paper defines a (branchingtime) noninterleaving semantics for ETLOTOS withou ..."
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Cited by 1 (0 self)
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One of the central objectives of the LOTOS restandardisation activity is to define an enhanced LOTOS language which supports realtime specification. The timed extension is based upon a timed LOTOS proposal ETLOTOS. This paper defines a (branchingtime) noninterleaving semantics for ETLOTOS without data. As a denotational model a suitable timed extension of Langerak's bundle event structures is used. For guarded recursive processes we show the consistency between our noninterleaving semantics and the ETLOTOS interleaving semantics. Since our semantical model does not have an explicit notion of the passage of time (as opposed to the interleaving semantics) we are able to handle unguarded recursion and Zenobehaviours in a perspicuous way. 1 Introduction The formal description technique LOTOS was standardised in 1987; for an introduction see [2]. However, it has been widely recognised that the language is deficient in a number of important respects. A particularly significant defic...
A Randomized Model for Communicating Embedded Systems
"... Nowadays, there is an intense research activity in designing systems that operate in real life, physical environments. This research is spanned by various areas in computer science and engineering: embedded systems, reactive systems, wireless communications, hybrid systems, stochastic processes, etc ..."
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Nowadays, there is an intense research activity in designing systems that operate in real life, physical environments. This research is spanned by various areas in computer science and engineering: embedded systems, reactive systems, wireless communications, hybrid systems, stochastic processes, etc. A severe limitation in the development of these systems is due to the mathematical foundation and complexity of the physical environment. Often, the physical environment is continuous and uncertain, and modelled in terms of continuous stochastic processes. These mathematics are quite different from the underlying mathematics of discrete controllers based on logic and algebra. In this paper, we propose a specification formalism called stochastic functional logic based on algebraic framework. This axiomatises and abstracts away advanced structures from functional and stochastic analysis. The definition of the logic mimics the practice in applied mathematics. This logic is integrated with a probabilistic process algebra to provide a specification framework for embedded systems. The integration mechanism is based on partial ordered sets. Moreover, we construct an energy integral to every stochastic functional logic specification. In this way, we combine the power of formal specification and stochastic analysis for the software development of embedded systems.