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12
A Denotational Model for Mobile PointtoPoint Dataflow Networks with Channel Sharing
, 1997
"... We present a fully abstract, denotational model for mobile, timed, nondeterministic dataflow networks whose components communicate in a pointtopoint fashion. In this model components and networks of components are represented by sets of stream processing functions. Each stream processing function ..."
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Cited by 22 (8 self)
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We present a fully abstract, denotational model for mobile, timed, nondeterministic dataflow networks whose components communicate in a pointtopoint fashion. In this model components and networks of components are represented by sets of stream processing functions. Each stream processing function is required to be strongly pulsedriven and privacy preserving. A function is strongly pulsedriven if it is contractive with respect to the metric on streams. This property guarantees the existence of unique fixpoints. The privacy preservation property can be thought of as an invariant specific to mobile pointtopoint systems. Firstly, it guarantees that a function never accesses, depends on or forwards a port whose name it does not already know. Secondly, it guarantees that at the same point in time no port is known to more than two components, namely the sender and the receiver. Our model allows the description of a wide variety of networks  in particular, the description of unbounded nondeterministic networks. We demonstrate some features of our model by specifying a communication central.
Automated Analysis of FaultTolerance in Distributed Systems
 In Proc. First ACM SIGPLAN Workshop on Automated Analysis of Software
, 1997
"... A method for automated analysis of faulttolerance of distributed systems is presented. It is based on a stream model of computation augmented with approximation constructs, and this facilitates efficient analysis. Analyses of a protocol for faulttolerant moving agents and a reliable broadcast prot ..."
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Cited by 4 (1 self)
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A method for automated analysis of faulttolerance of distributed systems is presented. It is based on a stream model of computation augmented with approximation constructs, and this facilitates efficient analysis. Analyses of a protocol for faulttolerant moving agents and a reliable broadcast protocol illustrate the method.
A Method and Tool for Analyzing FaultTolerance in Systems
, 1997
"... As computers are integrated into systems that have stringent faulttolerance requirements, there is a growing need for techniques to establish that these systems actually satisfy those requirements. Informal arguments do not supply the desired level of assurance for critical systems. This dissertat ..."
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Cited by 2 (2 self)
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As computers are integrated into systems that have stringent faulttolerance requirements, there is a growing need for techniques to establish that these systems actually satisfy those requirements. Informal arguments do not supply the desired level of assurance for critical systems. This dissertation presents a rigorous, automated approach to analyzing distributed systems, with a focus on checking faulttolerance requirements, and describes a prototype implementation of the analysis. The analysis is a novel hybrid of ideas from streamprocessing semantics of networks of processes, abstract interpretation of programs, and symbolic computation. The underlying principles of the analysis method are general, but specialized techniquessuch as the use of perturbations to represent changes to normal behavior caused by failuresare developed to deal e ciently with the types of systems and requirements that arise in establishing faulttolerance. The method is illustrated with three examples: the Oral Messages algorithm for Byzantine Agreement, due to Lamport, Shostak and Pease, a standard protocol for FIFO reliable broadcast, and a (subtly) awed protocol for faulttolerant moving agents. Biographical Sketch
Automated streambased analysis of faulttolerance
 In Fifth International Symposium on Formal Techniques in Real Time and Fault Tolerant Systems (FTRTFT
, 1998
"... Abstract. A rigorous, automated approach to analyzing faulttolerance of distributed systems is presented. The method is based on a stream model of computation that incorporates approximation mechanisms. One application is described: a protocol for faulttolerant moving agents. 1 ..."
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Cited by 2 (2 self)
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Abstract. A rigorous, automated approach to analyzing faulttolerance of distributed systems is presented. The method is based on a stream model of computation that incorporates approximation mechanisms. One application is described: a protocol for faulttolerant moving agents. 1
The Binary Decision Machine: A mathematical verification redone in PVS
 in PVS
, 1996
"... This paper presents a mathematical verification mechanically checked with the Prototype Verification System (PVS)[Owre96]. Prior to the mechanical proof a complete mathematical verification was done by us with use of the Funmath notation [Bout93]. One of the key ideas behind Funmath is the descri ..."
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Cited by 1 (1 self)
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This paper presents a mathematical verification mechanically checked with the Prototype Verification System (PVS)[Owre96]. Prior to the mechanical proof a complete mathematical verification was done by us with use of the Funmath notation [Bout93]. One of the key ideas behind Funmath is the description of mathematical notions as functions. The object of this verification is the binary decision machine (BDM) by R.T. Boute [Bout76], a hardware component which is used to realize systems described by binary decision diagrams [Lee59] [Aker78]. The proof in PVS was given with a conservative extension of the logic, i.e. no inconsistencies were introduced into the PVS logic. It is shown that this could easily be done (except in one case) given the original definitional style of the proof (i.e. using functions to describe objects), and the underlying (extensional) higherorder logic of PVS. 1 1 Introduction The object of this study is the binary decision machine (BDM) [Bout76], a bi...
Stream Processing II: An Alternative Algebraic Approach and the language ASTRAL
, 1995
"... We present a summary of [59] that develops the theoretical and practical tools necessary to provide a weak, secondorder algebraic approach to stream processing. This research is in contrast to existing techniques in the literature that are typically based on full secondorder semantic models. In ..."
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Cited by 1 (1 self)
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We present a summary of [59] that develops the theoretical and practical tools necessary to provide a weak, secondorder algebraic approach to stream processing. This research is in contrast to existing techniques in the literature that are typically based on full secondorder semantic models. In particular, we compare our approach with existing methods to demonstrate its advantages from the perspective of an analysis of computability issues and automated verification, and hence show that it provides the basis of an alternative general theory of stream processing. Finally, we discuss the development of the language ASTRAL based on this theory. 1 INTRODUCTION 2 1 Introduction 1.1 Definitions and Notation This paper is a companion to [60] that presents a detailed survey of the stream processing literature. As such we assume complete familiarity with [60] to which the reader is directed for all definitions and notation. 1.2 Motivation Our research into stream processing has bee...
Specification of RealTime and Hybrid Systems in FOCUS
 IN PROC. HYBRID AND REALTIME SYSTEMS
, 1996
"... Functional specifications in FOCUS have been used to specify and verify designs of a number of reactive, discrete systems. In this paper we extend this specification style to deal with realtime and hybrid systems. As mathematical foundation we employBanach's fixed point theory in metric spa ..."
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Functional specifications in FOCUS have been used to specify and verify designs of a number of reactive, discrete systems. In this paper we extend this specification style to deal with realtime and hybrid systems. As mathematical foundation we employBanach's fixed point theory in metric spaces. The goal is to show that the theory used for discrete functional specifications smoothly carries over to realtime and hybrid systems. An example of a thermostat specification illustrates the method.
Kahn's Networks of Processes as discrete analogues of Picard's Systems of Differential Equations
"... Anyone who has studied parallel programming with Kahn's networks of processes and also systems theory or control theory has noticed a strong similarity between the two. For one thing, both use similar diagrams, often with feedback, to express computations formed as compositions of incremental t ..."
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Anyone who has studied parallel programming with Kahn's networks of processes and also systems theory or control theory has noticed a strong similarity between the two. For one thing, both use similar diagrams, often with feedback, to express computations formed as compositions of incremental transforms. What is a mathematical basis for reconciling the two? Picard's theorem is a classical result in the theory of differential equations and integral equations. Kahn's theorem has similar renown in the theory of parallel programming, networks of processes, and stream processing. In this paper we clarify how these results are related, and show that Kahn's theorem and Picard's theorem are both special cases of a more general result. That we can do this may be surprising, since the foundations of the two theorems are quite different: metric function spaces and the fixed point theorem for contraction mappings in Picard's case, and complete partially ordered sets and the fixed point theorem for...
Formal Derivations Of Event Driven Programs
"... This paper continues along this line of investigation. In this paper a similar approach to formal system development is used to derive asynchronous distributed systems. With a functional calculus developed by Boute[Bou92], systems which process timed streams are formally introduced. Basic concepts o ..."
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This paper continues along this line of investigation. In this paper a similar approach to formal system development is used to derive asynchronous distributed systems. With a functional calculus developed by Boute[Bou92], systems which process timed streams are formally introduced. Basic concepts on the specification of systems, and the decomposition of them, are slightly modified to adapt to timed streams. In the second chapter a time domain is introduced upon which timed streams are defined. In the third chapter systems descriptions are introduced as relations between timed streams. The next chapter specifies an equivalence relation on these systems, which describes when a system may be used as a substitution of another system. Hereafter, the basic composition operators on systems are defined in the fifth chapter. In the next chapter some examples and transformation rules are given for the formal decomposition of system specificatons. Then it is shown how event handling programs can be derived in the next chapter. This paper concludes with the conclusions and possible future work. 1. The calculus