Results 1  10
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29
Trust evaluation in adhoc networks
 In 3rd ACM workshop on Wireless security
, 2004
"... An important concept in network security is trust, interpreted as a relation among entities that participate in various protocols. Trust relations are based on evidence related to the previous interactions of entities within a protocol. In this work, we are focusing on the evaluation process of trus ..."
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Cited by 71 (3 self)
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An important concept in network security is trust, interpreted as a relation among entities that participate in various protocols. Trust relations are based on evidence related to the previous interactions of entities within a protocol. In this work, we are focusing on the evaluation process of trust evidence in Ad Hoc Networks. Because of the dynamic nature of Ad Hoc Networks, trust evidence may be uncertain and incomplete. Also, no preestablished infrastructure can be assumed. The process is formulated as a path problem on a directed graph, where nodes represent entities, and edges represent trust relations. Using the theory of semirings, we show how two nodes can establish an indirect trust relation without previous direct interaction. The results are robust in the presence of attackers. We give intuitive requirements for any trust evaluation algorithm. The performance of the scheme is evaluated on three topologies.
On the Tractable Counting of Theory Models and its Application to Truth Maintenance and Belief Revision
 Journal of Applied NonClassical Logics
, 2000
"... We address the problem of counting the models of a propositional theory, under incremental changes to the theory. Specifically, we show that if a propositional theory is in a special form that we call smooth, deterministic, decomposable negation normal form (sdDNNF), then for any consistent set of ..."
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Cited by 60 (19 self)
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We address the problem of counting the models of a propositional theory, under incremental changes to the theory. Specifically, we show that if a propositional theory is in a special form that we call smooth, deterministic, decomposable negation normal form (sdDNNF), then for any consistent set of literals S, we can simultaneously count, in time linear in the size of , the models of: [ S; [ S [ flg: for every literal l 62 S; [ S n flg: for every literal l 2 S; [ S n flg [ f:lg: for every literal l 2 S.
A Logical Approach to Factoring Belief Networks
"... We have recently proposed a tractable logical form, known as deterministic, decomposable negation normal form (dDNNF). We have shown that dDNNF supports a number of logical operations in polynomial time, including clausal entailment, model counting, model enumeration, model minimization, and proba ..."
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Cited by 59 (13 self)
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We have recently proposed a tractable logical form, known as deterministic, decomposable negation normal form (dDNNF). We have shown that dDNNF supports a number of logical operations in polynomial time, including clausal entailment, model counting, model enumeration, model minimization, and probabilistic equivalence testing. In this paper, we discuss another major application of this logical form: the implementation of multilinear functions (of exponential size) using arithmetic circuits (that are not necessarily exponential). Specifically, we show that each multi–linear function can be encoded using a propositional theory, and that each dDNNF of the theory corresponds to an arithmetic circuit that implements the encoded multi–linear function. We discuss the application of these results to factoring belief networks, which can be viewed as multi–linear functions as has been shown recently. We discuss the merits of the proposed approach for factoring belief networks, and present experimental results showing how it can handle efficiently belief networks that are intractable to structure–based methods for probabilistic inference.
The Design and Analysis of BulkSynchronous Parallel Algorithms
, 1998
"... The model of bulksynchronous parallel (BSP) computation is an emerging paradigm of generalpurpose parallel computing. This thesis presents a systematic approach to the design and analysis of BSP algorithms. We introduce an extension of the BSP model, called BSPRAM, which reconciles sharedmemory s ..."
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Cited by 19 (1 self)
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The model of bulksynchronous parallel (BSP) computation is an emerging paradigm of generalpurpose parallel computing. This thesis presents a systematic approach to the design and analysis of BSP algorithms. We introduce an extension of the BSP model, called BSPRAM, which reconciles sharedmemory style programming with efficient exploitation of data locality. The BSPRAM model can be optimally simulated by a BSP computer for a broad range of algorithms possessing certain characteristic properties: obliviousness, slackness, granularity. We use BSPRAM to design BSP algorithms for problems from three large, partially overlapping domains: combinatorial computation, dense matrix computation, graph computation. Some of the presented algorithms are adapted from known BSP algorithms (butterfly dag computation, cube dag computation, matrix multiplication). Other algorithms are obtained by application of established nonBSP techniques (sorting, randomised list contraction, Gaussian elimination without pivoting and with column pivoting, algebraic path computation), or use original techniques specific to the BSP model (deterministic list contraction, Gaussian elimination with nested block pivoting, communicationefficient multiplication of Boolean matrices, synchronisationefficient shortest paths computation). The asymptotic BSP cost of each algorithm is established, along with its BSPRAM characteristics. We conclude by outlining some directions for future research.
A Differential Semantics for Jointree Algorithms
"... Darwiche has recently proposed the representation of a belief network as a multivariate polynomial, allowing one to reduce probabilistic inference into a process of evaluating and dierentiating polynomials. ..."
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Cited by 16 (9 self)
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Darwiche has recently proposed the representation of a belief network as a multivariate polynomial, allowing one to reduce probabilistic inference into a process of evaluating and dierentiating polynomials.
Fine grained access control with trust and reputation management for globus
 In GADA 2007, To appear Lecture Notes in Computer Science
, 2007
"... Abstract. We propose an integrated architecture, extending a framework for fine grained access control of Grid computational services, with an inference engine managing reputation and trust management credentials. Also, we present the implementation of the proposed architecture, with preliminary per ..."
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Cited by 16 (7 self)
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Abstract. We propose an integrated architecture, extending a framework for fine grained access control of Grid computational services, with an inference engine managing reputation and trust management credentials. Also, we present the implementation of the proposed architecture, with preliminary performance figures. 1
Parameter learning for relational bayesian networks
 In Proceedings of the International Conference in Machine Learning
, 2007
"... We present a method for parameter learning in relational Bayesian networks (RBNs). Our approach consists of compiling the RBN model into a computation graph for the likelihood function, and to use this likelihood graph to perform the necessary computations for a gradient ascent likelihood optimizati ..."
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Cited by 13 (2 self)
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We present a method for parameter learning in relational Bayesian networks (RBNs). Our approach consists of compiling the RBN model into a computation graph for the likelihood function, and to use this likelihood graph to perform the necessary computations for a gradient ascent likelihood optimization procedure. The method can be applied to all RBN models that only contain differentiable combining rules. This includes models with nondecomposable combining rules, as well as models with weighted combinations or nested occurrences of combining rules. Experimental results on artificial random graph data explores the feasibility of the approach both for complete and incomplete data. 1.
Preferencebased search in state space graphs
 In Proceedings of AAAI02
, 2002
"... The aim of this paper is to introduce a general framework for preferencebased search in state space graphs with a focus on the search of the preferred solutions. After introducing a formal definition of preferencebased search problems, we introduce the PBA ∗ algorithm, a generalization of the A ∗ ..."
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Cited by 12 (5 self)
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The aim of this paper is to introduce a general framework for preferencebased search in state space graphs with a focus on the search of the preferred solutions. After introducing a formal definition of preferencebased search problems, we introduce the PBA ∗ algorithm, a generalization of the A ∗ algorithm, designed to process quasitransitive preference relations defined over the set of solutions. Then, considering a particular subclass of preference structures characterized by two axioms called Weak Preadditivity and Monotonicity, weestablish termination, completeness and admissibility results for PBA ∗.Wealsoshowthat previous generalizations of A ∗ are particular instances of PBA ∗.Theinterest of our algorithm is illustrated on a preferencebased web access problem.
Timetable Information: Models and Algorithms
, 2006
"... We give an overview of models and efficient algorithms for optimally solving timetable information problems like “given a departure and an arrival station as well as a departure time, which is the connection that arrives as early as possible at the arrival station?” Two main approaches that transfor ..."
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Cited by 9 (7 self)
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We give an overview of models and efficient algorithms for optimally solving timetable information problems like “given a departure and an arrival station as well as a departure time, which is the connection that arrives as early as possible at the arrival station?” Two main approaches that transform the problems into shortest path problems are reviewed, including issues like the modeling of realistic details (e.g., train transfers) and further optimization criteria (e.g., the number of transfers). An important topic is also multicriteria optimization, where in general all attractive connections with respect to several criteria shall be determined. Finally, we discuss the performance of the described algorithms, which is crucial for their application in a real system.