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The PEPA Workbench: A Tool to Support a Process Algebrabased Approach to Performance Modelling
 In Proceedings of the Seventh International Conference on Modelling Techniques and Tools for Computer Performance Evaluation, number 794 in Lecture Notes in Computer Science
, 1994
"... . In this paper we present a new technique for performance modelling and a tool supporting this approach. Performance Evaluation Process Algebra (PEPA) [1] is an algebraic language which can beused to build models of computer systems which capture information about the performance of the system. The ..."
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Cited by 161 (61 self)
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. In this paper we present a new technique for performance modelling and a tool supporting this approach. Performance Evaluation Process Algebra (PEPA) [1] is an algebraic language which can beused to build models of computer systems which capture information about the performance of the system. The PEPA language serves two purposes as a formal description language for computer system models. The performancerelated information in the model may be used to predict the performance of the system whereas the behavioural information in the model may be exploited when reasoning about the functional behaviour of the system (e.g. when finding deadlocks or when exhibiting equivalences between subcomponents). In this paper we concentrate on the performance aspects of the language. A method of reasoningaboutPEPA modelsproceedsby considering the derivation graph obtained from the model using the underlying operational semantics of the PEPA language. The derivation graph is systematically reduced ...
Forward and Backward Simulations  Part II: TimingBased Systems
 Information and Computation
, 1995
"... A general automaton model for timingbased systems is presented and is used as the context for developing a variety of simulation proof techniques for such systems. These techniques include (1) refinements, (2) forward and backward simulations, (3) hybrid forwardbackward and backwardforward sim ..."
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Cited by 85 (29 self)
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A general automaton model for timingbased systems is presented and is used as the context for developing a variety of simulation proof techniques for such systems. These techniques include (1) refinements, (2) forward and backward simulations, (3) hybrid forwardbackward and backwardforward simulations, and (4) history and prophecy relations. Relationships between the different types of simulations, as well as soundness and completeness results, are stated and proved. These results are (with one exception) analogous to the results for untimed systems in Part I of this paper. In fact, many of the results for the timed case are obtained as consequences of the analogous results for the untimed case.
Blending ObjectZ and Timed CSP: An introduction to TCOZ
 THE 20TH INTERNATIONAL CONFERENCE ON SOFTWARE ENGINEERING (ICSE’98
, 1997
"... ObjectZ is an extension to the Z language designed to facilitate specification in an objectoriented style. It is an excellent tool for modeling data and algorithms, but its object semantics are single threaded and operations are atomic. Therefore, it is difficult to use ObjectZ to capture the beh ..."
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Cited by 51 (13 self)
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ObjectZ is an extension to the Z language designed to facilitate specification in an objectoriented style. It is an excellent tool for modeling data and algorithms, but its object semantics are single threaded and operations are atomic. Therefore, it is difficult to use ObjectZ to capture the behaviour of concurrent realtime reactive systems. On the other hand, Timed CSP is good at modeling realtime concurrent behaviour, but has little support for modeling the state of a complex system. This paper introduces a blending of ObjectZ and Timed CSP, known as TCOZ. The blended notation is particularly suited for specifying complex systems whose components have their own thread of control.
The nature of synchronisation
 Proceedings of the Second International Workshop on Process Algebras and Performance Modelling
, 1994
"... In each of the current stochastic process algebras all noncompetitive interactions between components or agents are modelled using a single combinator, variously called the parallel, synchronisation or cooperation operator. This paper aims to compare the definitions of this combinator which have be ..."
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Cited by 43 (14 self)
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In each of the current stochastic process algebras all noncompetitive interactions between components or agents are modelled using a single combinator, variously called the parallel, synchronisation or cooperation operator. This paper aims to compare the definitions of this combinator which have been used; in particular, looking at the different ways in which rates are associated with the actions which result from such interactions. The implications of the chosen definitions, from a modelling point of view, will be described. When we consider concrete systems rather than abstract representations many different types of interactions between systems are exhibited. Some of these possible interactions are presented in the latter half of the paper and we analyse the extent to which these can be captured using the combinators available in the SPA languages. To conclude some observations about current modelling practice are made together with suggestions of potential extensions to the set of combinators. 1
A Graphical Parallel Composition Operator for Process Algebras
 In Joint International Conference on Formal Description Techniques for Distributed Systems and Communication Protocols, and Protocol Specification, Testing, and Verification (FORTE/PSTV’99
, 1998
"... . Process algebras are suitable for describing networks of communicating processes. In most process algebras, the description of such networks is achieved using parallel composition operators. Noticing that the parallel composition operators commonly found in usual process algebras are often lim ..."
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Cited by 23 (4 self)
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. Process algebras are suitable for describing networks of communicating processes. In most process algebras, the description of such networks is achieved using parallel composition operators. Noticing that the parallel composition operators commonly found in usual process algebras are often limited in expressiveness and/or nonintuitive for nonexpert users, we propose a new parallel operator that allows networks of communicating processes to be described easily, in a simple and wellstructured manner. We illustrate on various examples (tokenring network, clientserver protocol, chessboard grid) the theoretical and practical merits of our operator. 1 Introduction Process algebras have been designed as a theoretical framework for the study of concurrency. Classical examples of process algebras are: ACP [1], CCS [24, 25], CSP [15], MEIJE [7], etc. There also exist specification languages, which combine process algebraic concepts with features borrowed from (functional or imper...
Combining Specification Techniques for Processes, Data and Time
 Nordic Journal of Computing
, 2002
"... We present a new combination CSPOZDC of three well researched formal techniques for the specification of processes, data and time: CSP [17], ObjectZ [36], and Duration Calculus [40]. The emphasis is on a smooth integration of the underlying semantic models and its use for verifying properties ..."
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Cited by 22 (4 self)
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We present a new combination CSPOZDC of three well researched formal techniques for the specification of processes, data and time: CSP [17], ObjectZ [36], and Duration Calculus [40]. The emphasis is on a smooth integration of the underlying semantic models and its use for verifying properties of CSPOZDC specifications by a combined application of the modelcheckers FDR [29] for CSP and UPPAAL [1] for Timed Automata. This approach is applied to part of a case study on radio controlled railway crossings.
Discrete Analysis of Continuous Behaviour in RealTime Concurrent Systems
, 2001
"... This thesis concerns the relationship between continuous and discrete modelling paradigms for timed concurrent systems, and the exploitation of this relationship towards applications, in particular model checking. The framework we have chosen is Reed and Roscoe's process algebra Timed CSP, in w ..."
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Cited by 19 (7 self)
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This thesis concerns the relationship between continuous and discrete modelling paradigms for timed concurrent systems, and the exploitation of this relationship towards applications, in particular model checking. The framework we have chosen is Reed and Roscoe's process algebra Timed CSP, in which semantic issues can be examined from both a denotational and an operational perspective. The continuoustime model we use is the timed failures model; on the discretetime side, we build a suitable model in a CSPlike setting by incorporating a distinguished tock event to model the passage of time. We study the connections between these two models and show that our framework can be used to verify certain speci cations on continuoustime processes, by building upon and extending results of Henzinger, Manna, and Pnueli's. Moreover, this veri cation can in many cases be carried out directly on the model checker FDR . Results are illustrated with a small railway level crossing case study. We also construct a second, more sophisticated discretetime model which reects continuous behaviour in a manner more consistent with one's intuition, and show that our results carry over this second model as well.
Sensors and Actuators in TCOZ
 FM’99: WORLD CONGRESS ON FORMAL METHODS, LECT. NOTES IN COMPUT. SCI
, 1999
"... Timed Communicating Object Z (TCOZ) combines ObjectZ's strengths in modeling complex data and algorithms with Timed CSP's strengths in modeling realtime concurrency. TCOZ inherits CSP's channelbased communication mechanism, in which messages represent discrete synchronisations ..."
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Cited by 16 (3 self)
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Timed Communicating Object Z (TCOZ) combines ObjectZ's strengths in modeling complex data and algorithms with Timed CSP's strengths in modeling realtime concurrency. TCOZ inherits CSP's channelbased communication mechanism, in which messages represent discrete synchronisations between processes. The purpose of most control systems is to observe and control analog components. In such cases, the interface between the control system and the controlled systems cannot be satisfactorily described using the channel mechanism. In order to address this problem, TCOZ is extended with continuousfunction interface mechanisms inspired by process control theory, the sensor and the actuator. The utility of these new mechanisms is demonstrated through their application to the design of an automobile cruise control system.
A timed verification of the IEEE 1394 leader election protocol
 FORMAL METHODS IN SYSTEM DESIGN
, 2001
"... ..."
Timed systems in SAL
 Computer Science Laboratory
, 2004
"... The Symbolic Analysis Laboratory (SAL) is a set of tools for the specification, exploration, and verification of statetransition systems. SAL includes symbolic modelchecking tools based on solvers and decision procedures for linear arithmetic, uninterpreted functions, and propositional logic, amon ..."
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Cited by 15 (2 self)
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The Symbolic Analysis Laboratory (SAL) is a set of tools for the specification, exploration, and verification of statetransition systems. SAL includes symbolic modelchecking tools based on solvers and decision procedures for linear arithmetic, uninterpreted functions, and propositional logic, among others. This enables the analysis of a variety of infinitestate systems. In particular, SAL can be used to model and verify timed systems, which combine realvalued and discrete state variables. This document reports on several examples and experiments in modeling and verification of timed system in SAL. Different specification approaches are presented and compared, from a direct encoding of traditional timed automata to a novel modeling method based on event calendars. We present verification techniques that rely on induction and abstraction, and show how these techniques are efficiently supported by the SAL symbolic modelchecking tools.