3,203 research outputs found
Formal mechanization of device interactions with a process algebra
The principle emphasis is to develop a methodology to formally verify correct synchronization communication of devices in a composed hardware system. Previous system integration efforts have focused on vertical integration of one layer on top of another. This task examines 'horizontal' integration of peer devices. To formally reason about communication, we mechanize a process algebra in the Higher Order Logic (HOL) theorem proving system. Using this formalization we show how four types of device interactions can be represented and verified to behave as specified. The report also describes the specification of a system consisting of an AVM-1 microprocessor and a memory management unit which were verified in previous work. A proof of correct communication is presented, and the extensions to the system specification to add a direct memory device are discussed
On Modelling and Analysis of Dynamic Reconfiguration of Dependable Real-Time Systems
This paper motivates the need for a formalism for the modelling and analysis
of dynamic reconfiguration of dependable real-time systems. We present
requirements that the formalism must meet, and use these to evaluate well
established formalisms and two process algebras that we have been developing,
namely, Webpi and CCSdp. A simple case study is developed to illustrate the
modelling power of these two formalisms. The paper shows how Webpi and CCSdp
represent a significant step forward in modelling adaptive and dependable
real-time systems.Comment: Presented and published at DEPEND 201
Reexamination of Quantum Bit Commitment: the Possible and the Impossible
Bit commitment protocols whose security is based on the laws of quantum
mechanics alone are generally held to be impossible. In this paper we give a
strengthened and explicit proof of this result. We extend its scope to a much
larger variety of protocols, which may have an arbitrary number of rounds, in
which both classical and quantum information is exchanged, and which may
include aborts and resets. Moreover, we do not consider the receiver to be
bound to a fixed "honest" strategy, so that "anonymous state protocols", which
were recently suggested as a possible way to beat the known no-go results are
also covered. We show that any concealing protocol allows the sender to find a
cheating strategy, which is universal in the sense that it works against any
strategy of the receiver. Moreover, if the concealing property holds only
approximately, the cheat goes undetected with a high probability, which we
explicitly estimate. The proof uses an explicit formalization of general two
party protocols, which is applicable to more general situations, and a new
estimate about the continuity of the Stinespring dilation of a general quantum
channel. The result also provides a natural characterization of protocols that
fall outside the standard setting of unlimited available technology, and thus
may allow secure bit commitment. We present a new such protocol whose security,
perhaps surprisingly, relies on decoherence in the receiver's lab.Comment: v1: 26 pages, 4 eps figures. v2: 31 pages, 5 eps figures; replaced
with published version; title changed to comply with puzzling Phys. Rev.
regulations; impossibility proof extended to protocols with infinitely many
rounds or a continuous communication tree; security proof of decoherence
monster protocol expanded; presentation clarifie
Issues about the Adoption of Formal Methods for Dependable Composition of Web Services
Web Services provide interoperable mechanisms for describing, locating and
invoking services over the Internet; composition further enables to build
complex services out of simpler ones for complex B2B applications. While
current studies on these topics are mostly focused - from the technical
viewpoint - on standards and protocols, this paper investigates the adoption of
formal methods, especially for composition. We logically classify and analyze
three different (but interconnected) kinds of important issues towards this
goal, namely foundations, verification and extensions. The aim of this work is
to individuate the proper questions on the adoption of formal methods for
dependable composition of Web Services, not necessarily to find the optimal
answers. Nevertheless, we still try to propose some tentative answers based on
our proposal for a composition calculus, which we hope can animate a proper
discussion
Expectation Propagation for Approximate Inference: Free Probability Framework
We study asymptotic properties of expectation propagation (EP) -- a method
for approximate inference originally developed in the field of machine
learning. Applied to generalized linear models, EP iteratively computes a
multivariate Gaussian approximation to the exact posterior distribution. The
computational complexity of the repeated update of covariance matrices severely
limits the application of EP to large problem sizes. In this study, we present
a rigorous analysis by means of free probability theory that allows us to
overcome this computational bottleneck if specific data matrices in the problem
fulfill certain properties of asymptotic freeness. We demonstrate the relevance
of our approach on the gene selection problem of a microarray dataset.Comment: Both authors are co-first authors. The main body of this paper is
accepted for publication in the proceedings of the 2018 IEEE International
Symposium on Information Theory (ISIT
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Graph models for reachability analysis of concurrent programs
Reachability analysis is an attractive technique for analysis of concurrent programs because it is simple and relatively straightforward to automate, and can be used in conjunction with model-checking procedures to check for application-specific as well as general properties. Several techniques have been proposed differing mainly on the model used; some of these propose the use of flowgraph based models, some others of Petri nets.This paper addresses the question: What essential difference does it make, if any, what sort of finite-state model we extract from program texts for purposes of reachability analysis? How do they differ in expressive power, decision power, or accuracy? Since each is intended to model synchronization structure while abstracting away other features, one would expect them to be roughly equivalent.We confirm that there is no essential semantic difference between the most well known models proposed in the literature by providing algorithms for translation among these models. This implies that the choice of model rests on other factors, including convenience and efficiency.Since combinatorial explosion is the primary impediment to application of reachability analysis, a particular concern in choosing a model is facilitating divide-and-conquer analysis of large programs. Recently, much interest in finite-state verification systems has centered on algebraic theories of concurrency. Yeh and Young have exploited algebraic structure to decompose reachability analysis based on a flowgraph model. The semantic equivalence of graph and Petri net based models suggests that one ought to be able to apply a similar strategy for decomposing Petri nets. We show this is indeed possible through application of category theory
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