Haut PDF A modal approach to model computational trust

A modal approach to model computational trust

A modal approach to model computational trust

Our work is divided into three main chapter. Our first chapter takes the form of a global survey on computational trust that presents differ- ent perspective on how to model trust, by presenting the modelization process as composed of three parts. At first, an intermediary general trust theory need to be defined. Such semi-formal characterization is conducted either by describing trust properties, or relating trust to a set of concepts that are used to understand how trust is used. While presenting a set of trust theories, we emphasize two of the most influen- tial trust definitions that we encountered, Castelfranchi & Falcone [24] and Marsh [49] models. The second step in modeling trust is to specify a field of application, as a way to describe both the observation and a priori assumption, that are used to assess trust, and the decision process that will use trust to guide interaction. The third step cor- responds to the selection of a framework in which a trust theory will be instantiated, in this section we present trust models, categorized by such framework of applications.
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A coherent computational Approach to model the bottom-up visual attention.

A coherent computational Approach to model the bottom-up visual attention.

Most recent computational models of visual attention can be placed in two categories. A recent trend concerns a statistical signal-based approach [2] which consists of automatically predicting salient regions of the visual scene by directly using image statistics at the point of gaze. In fact, several studies have recently reported [3], [4], [5] that the human fixation regions present higher spatial contrast and spatial entropy than random fixation regions. These studies show that human eyes movements are not necessarily random but rather driven by particular features. The second category consists of models [6], [7], [8], [9], [10], [11] built around two important concepts: the Feature Integration Theory (FIT) from Treisman and Gelade [12] and a neurally plausible architecture proposed by Koch and Ullman [13]. The FIT suggests that visual information is analyzed in parallel from different maps. These maps are retinotopically organized according to locations in our visual field. There is a map for each early visual feature. From this theory, several frameworks for simulating human visual attention have been designed. The most interesting one has been proposed by Koch and Ullman [13]. Their framework is based on the concept of saliency map which is a two-dimensional topo- graphic representation of conspicuity for every pixels in the image. Fig. 1 illustrates the general synoptic of their model. It mainly consists of early visual features extraction, feature maps building, and feature map fusion.
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A multi-modal approach using a non-parametric model to extract fetal ECG

A multi-modal approach using a non-parametric model to extract fetal ECG

This method is a multi-channel method as the classical methods like adaptive filters; however despite adaptive filters this is a non-linear method. The method also provides a multi- modal approach to use the PCG data in modeling fetal ECG. This approach first validates the relationship between these two data, and second it gives better results in extraction of fetal ECG when having a separate model for fetus instead of using only one model for mother, as validated in section 3. In the same section we have shown that the reference signals can be replaced by 1-bit reference without a noticeable change in the results. Using 1-bit reference signals have several advan- tages: first of all, they are easier to record with 1-bit ADCs, secondly, they are less memory consuming, and finally they can be processed faster in time.
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A model order reduction approach to create patient-specific mechanical models of human liver in computational medicine applications.

A model order reduction approach to create patient-specific mechanical models of human liver in computational medicine applications.

4. Discussion Globally, the error done in the leave-one-out tests comes from the reconstruction from a limited number of modes. This error could be decreased by using more modes to represent the shape. However, more modes means more computations for the SSL and a more difficult convergence. Here it is difficult to go further than 10 shape modes for the SSL without reaching high computational times. Concerning the SSL error, the main flaw lies in the choice of the parameters subspace. As shown in the previous section the SSL error mainly comes from reconstructed shapes taken out of the pa- rameters subspace, and their number increases with the number of modes. Nonetheless, this error stays within acceptable range and for shapes taken inside the parameters subspace a really high fi- delity reconstruction is done. Moreover, a consequent speedup is achieved thanks to MOR while taking into account the same phys- ical equations than the initial FE problem, without making addi- tional assumptions. As noticed in Section 3 this initial model is al- ready computed relatively fast, and with an implementation in a low-level programming language and a more powerful hardware a computation could certainly be done in near real-time ( ∼ 1s), which would be sufficient for breathing applications and would question the use of a pROM. As mentioned before the use case pre- sented in this article is a simple example to illustrate the method and more complex situations involving non-linear behaviors should be tested. Anyhow, the pROM approach still has the advantage of requiring simple computational means, which is important to compensate for the lack of advanced hardware in clinical environ- ments.
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A model order reduction approach to create patient-specific mechanical models of human liver in computational medicine applications.

A model order reduction approach to create patient-specific mechanical models of human liver in computational medicine applications.

4. Discussion Globally, the error done in the leave-one-out tests comes from the reconstruction from a limited number of modes. This error could be decreased by using more modes to represent the shape. However, more modes means more computations for the SSL and a more difficult convergence. Here it is difficult to go further than 10 shape modes for the SSL without reaching high computational times. Concerning the SSL error, the main flaw lies in the choice of the parameters subspace. As shown in the previous section the SSL error mainly comes from reconstructed shapes taken out of the pa- rameters subspace, and their number increases with the number of modes. Nonetheless, this error stays within acceptable range and for shapes taken inside the parameters subspace a really high fi- delity reconstruction is done. Moreover, a consequent speedup is achieved thanks to MOR while taking into account the same phys- ical equations than the initial FE problem, without making addi- tional assumptions. As noticed in Section 3 this initial model is al- ready computed relatively fast, and with an implementation in a low-level programming language and a more powerful hardware a computation could certainly be done in near real-time ( ∼ 1s), which would be sufficient for breathing applications and would question the use of a pROM. As mentioned before the use case pre- sented in this article is a simple example to illustrate the method and more complex situations involving non-linear behaviors should be tested. Anyhow, the pROM approach still has the advantage of requiring simple computational means, which is important to compensate for the lack of advanced hardware in clinical environ- ments.
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A non‐biased trust model for wireless mesh networks

A non‐biased trust model for wireless mesh networks

values as seen by the low dip just below the trust threshold boundary of 0.5. The aggregated trust value is 0.495 indicating that the node is untrustworthy. This is due to the choice of the weighting factors in the linear function which we configure as 0.5 in this comparative study. We note that the performance of the linear opinion pooling technique could be improved by using a heavier weight on the direct trust component of the linear function. However, relying too much on the direct trusts would downplay the influence of the indirect trusts towards the final trust aggregation. To resolve this problem, R. Chen et al. [20] has proposed to set the weights dynamically in response to past node changes and environmental changes. However, this approach is not indicative enough to model the actual behavior of a node and can only be regarded as an estimate. The other reason for the small trust variation as seen from the flat curve is that all the indirect trust values are first combined into a single aggregate indirect trust value using the weighted average approach before it is merged with the direct trust value. Therefore, the impact of the aggregated indirect trust is very small in comparison to direct trust observations. Figure 4 shows the trust relationship when there are ballot-stuffing attackers in the network. Similar results are observed where the DS-Trust model is able to tolerate up to ten ballot-stuffing attackers before it succumbs to the false recommendations while the rest of the scheme are vulnerable to a small number of ballot-stuffing attackers. In figure 4, the aggregated trust
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A Log Auditing Approach for Trust Management in Peer-to-Peer Collaboration

A Log Auditing Approach for Trust Management in Peer-to-Peer Collaboration

Equipes-Projets SCORE Rapport de recherche n° 7472 — Decembre 2010 — 13 pages Abstract: Nowadays we are faced with an increasing popularity of social software including wikis, blogs, micro-blogs and online social networks such as Facebook and MySpace. Unfortunately, the mostly used social services are centralized and personal information is stored at a single vendor. This results in potential privacy problems as users do not have much control over how their pri- vate data is disseminated. To overcome this limitation, some recent approaches envisioned replacing the single authority centralization of services by a peer- to-peer trust-based approach where users can decide with whom they want to share their private data. In this peer-to-peer collaboration it is very difficult to ensure that after data is shared with other peers, these peers will not misbehave and violate data privacy. In this paper we propose a mechanism that addresses the issue of data privacy violation due to data disclosure to malicious peers. In our approach trust values between users are adjusted according to their previ- ous activities on the shared data. Users share their private data by specifying some obligations the receivers must follow. We log modifications done by users on the shared data as well as the obligations that must be followed when data is shared. By a log-auditing mechanism we detect users that misbehaved and we adjust their associated trust values by using any existing decentralized trust model.
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A Trust-based Decision-making Approach Applied to Agents in Collaborative Environments

A Trust-based Decision-making Approach Applied to Agents in Collaborative Environments

(Castelfranchi and Falcone, 2010) propose a com- putational model of social trust. In this model the trustor’s beliefs about the trustee’s motivation, capac- ity and opportunity to do a task, are used to decide over delegation. In this model the motivation belief is very difficult to compute without a context: for example it is deduced from the trustee’s profession (e.g. a doctor is believed to be motivated to help her patients), or from the trustee’s relationship with the trustor (e.g. friends are supposed to be willing to help one another). Without this context, motivation is diffi- cult to explain, yet agent behavior needs to be explain- able to the trainee. The integrity and benevolence di-
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Uncertainty in biology: a computational modeling approach

Uncertainty in biology: a computational modeling approach

However these biomedical problems are inherently complex with a myriad of influencing factors, which strongly complicates the model building and validation process. This book wants to address four main issues related to the building and validation of computational models of biomedical processes:

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Design for assembly : a computational approach to construct interlocking wooden frames

Design for assembly : a computational approach to construct interlocking wooden frames

Given a three dimensional digital model of an interlocking frame, the feasibility of the disassembly sequence can be assessed by analyzing the geometric contact constraints b[r]

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T2D: A Peer to Peer trust management system based on Disposition to Trust

T2D: A Peer to Peer trust management system based on Disposition to Trust

Lyon, France lionel.brunie@liris.cnrs.fr ABSTRACT While the trust paradigm is essential to broadly extend the communication between the environment’s actors, the eval- uation of trust becomes a challenge when confronted with initializing the trust relationship and validating the transi- tive propriety of trust. Whether between users or between organizations, existing solutions work to create for peer to peer networks, flexible and decentralized security mecha- nisms with trust approach. However, we have noticed that the trust management systems do not make the most of the subjectivity, more specifically, the notion of Disposition to Trust although this aspect of subjectivity has a strong influence on how to assess direct and a transitive trust. For this reason in our study, we tackle this problem by intro- ducing a new distributed trust model called T2D (Trust to Distrust) which is designed to incorporate the follow- ing contributions : (i) A behavior model which represents the Disposition to Trust ; (ii) Initialization of trust relation- ship (direct and transitive) according to the defined behavior model.
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Algebraic approach to modal extensions of Łukasiewicz logics

Algebraic approach to modal extensions of Łukasiewicz logics

The game has also been considered by many-valued logicians as a way to give a concrete interpretation of Šukasiewicz nitely-valued calculi and their associated algebras (see [45]). Up to now, mathematician have modeled the game in a simple way by coding algebraically questions and answers. We start by introducing this interpretation, which is due to Mundici, and then add to it a dynamic layer in order to model the interactions between the two gamers. 1.3.1. Algebraic approach of the states of knowledge. We call the rst gamer (the one who chooses a number and can lie) Pinocchio, and the second gamer Geppetto. Let us denote by M the search space, i.e., the nite set of integers (or whatever) in which Pinocchio can pick up his number. Let us also assume that Pinocchio can lie n − 1 times (where n ≥ 1).
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A computational approach for obstruction-free photography

A computational approach for obstruction-free photography

3 Problem Setup Figure 2 shows our image formation model. A camera is imaging a scene through a visual obstruction, which can be either a reflective object, such as glass, or an opaque object, such as a fence. In order to remove the artifacts—either the obstruction itself, or the reflec- tion introduced by the obstruction—the user captures a sequence of images while moving the camera. In this paper we assume that both the obstruction and background objects remain roughly static dur- ing the capture. If the obstruction is opaque (a fence, for example), we further require that each pixel in the background scene would be visible (not occluded by the obstruction) in at least one frame in the sequence, so that its information could be recovered. We also assume that the obstruction (or the reflected content) is not too close to the background, so that when moving the camera there would be sufficient difference between the motions of the two layers. In this paper, we use a lower-case letter a to denote a scalar, a normal capital letter A to denote a vector, and a bold capital letter A to denote a matrix. We denote the matrix product as AB, where
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A generic approach to model generation operations

A generic approach to model generation operations

4.4.3. Results summary The approach is functional but suffers from computational is- sues. Obviously, computation times are highly impacted by the specifications. The running example strongly constraints the result, while the state machines example is clearly an easier problem. The instances size and the chosen scenario are also an important factor. This combinatorial approach seems generally more fitted for syn- chronization than classical transformations or generations. Finally a number of limitations stem from the chosen solver backend. In- deed, the Alloy/SAT combination shows its limits both in the size of problems it can handle, which can be mostly tied to the re- quired scope issues, and in the types of operations that can be used in the specifications. Indeed arithmetic operations are sup- ported but costly, while string manipulations are strictly limited to plain equality. We believe this confirms the relevance of our solver-agnostic abstraction. On one hand it eases the development of alternative backends since only a part of the model search chain needs be defined. On the other hand it allows the user to switch
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Trust Approach Based on User's Activities

Trust Approach Based on User's Activities

instances of data (including application codes) are stored and artifacts (softwares) are running. S OCIO P ATH also describes the relations between the different components of the two worlds. Enriched with deduction rules, the S OCIO P ATH meta-model allows to underline and discover chains of access and control relations between the actors and the digital resources in a system. A user may completely trust a person in a field, where she does not trust the same person at all in another field, for example, a user may trust a person in the quality of services she offers, but not in keeping her data private. The Implicit relations of access and control in a system allows the user to know who are the persons who might access or control her data, thus considering the privacy as a factor to evaluate the trustworthy of these persons.
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Multimodal Approach for Emotion Recognition Using a Formal Computational Model

Multimodal Approach for Emotion Recognition Using a Formal Computational Model

Figure 3. The dimensional approach Representing emotional states in technological environments is necessarily based on some representation format. Ball and Breese (Ball & Breese, 1999) have proposed a model of emotional states based on the Bayesian networks, which is designed to estimate the emotional state of a user interacting with a conversational compute. López an all (Lopez, Cearreta, Garay- Vitoria, Lopez de Ipiňae, & Beristain, 2009) have proposed a model based on a generic ontology for describing emotions and their detection and expression systems taking contextual and multimodal elements into account. In earlier work (Tayari Meftah, Thanh, & Ben Amar, 2010; Tayari Meftah et al., 2011) we have proposed an algebraic model for the representation and the exchange of emotions. Our model permits to model not only the basic emotions (e.g., anger, sadness, fear) but also different types of complex emotions like simulated and masked emotions.
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A Computational Model of Trust Based on Message Content and Source

A Computational Model of Trust Based on Message Content and Source

1. INTRODUCTION The extent to which new information is accepted by an agent directly depends on the content of the new claim and on how much the agent trusts the source providing it. However, trust may also be influenced by information content. Indeed, even tough I might not particularly trust a source, if it provides me a claim which is consistent with my beliefs, I will not change my beliefs. However, my degree of trust for that source may increase. Trust depends thus on the agent’s own beliefs in general and, in particular, on the agent’s opinion about the capability of the source to convey useful information. In real-world situations, an agent’s beliefs about a source may be incomplete, for they may derive from the opinions of other (partially) known agents and the agent may have had few (or none) exchanges with the source.
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A MODAL APPROACH TO THE NUMERICAL SIMULATION OF A STRING VIBRATING AGAINST AN OBSTACLE: APPLICATIONS TO SOUND SYNTHESIS

A MODAL APPROACH TO THE NUMERICAL SIMULATION OF A STRING VIBRATING AGAINST AN OBSTACLE: APPLICATIONS TO SOUND SYNTHESIS

In this study, we present a conservative numerical scheme to model a stiff damped string vibrating against an arbitrarily shaped obstacle. The key features of the scheme are as follows. A modal expansion is used as a starting point for the linear case (i.e., in the absence of contact). By using an equal number of modes and dis- cretization points, a linear transformation relates the spatial dis- placement and the modal coordinates, so that the contact force is treated directly with the displacement. Finally a regularized contact force together with an energy-conserving time-stepping scheme are implemented. Eigenfrequencies and damping parame- ters of the string can be adjusted at ease, and in particular accord- ing to experimental measurements so that sound synthesis can be more realistic.
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A Certified Trust Region Reduced Basis Approach to PDE-Constrained Optimization

A Certified Trust Region Reduced Basis Approach to PDE-Constrained Optimization

also note that Lipschitz continuity follows from the boundedness of the sensitivity derivative which, given our assumptions, is shown for the parabolic state equation in [13]. 3. Reduced basis method. The RB method is a projection-based model re- duction method for parametrized PDEs [27]. Traditionally, it consists of an expensive, time-consuming offline phase, in which the reduced basis is built, and an inexpensive online phase, during which the prebuilt RB may be exploited for rapid and certified simulations of the PDE at any parameter within the admissible parameter domain. In this section, we present primal-dual RB approximations and associated novel a pos- teriori error estimation procedures for the elliptic and parabolic PDE-constrained parameter optimization problems introduced in the last section. To this end, we em- ploy the RB approximations as surrogate models in the optimization problems (10) and (14) and develop new rigorous and efficiently evaluable error bounds for the cost functional and its gradient. In this work, we leverage these new error bounds to break from the offline/online paradigm in the optimization; i.e., we build the RB approx- imation on the fly during the iterative optimization procedure. Our error bounds guide the RB updates and at the same time allow us to guarantee convergence of the surrogate optimization to the (unknown) optimal solution of the original (FE) optimization problem. We note, however, that the results presented here also apply to the traditional offline/online RB setting.
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Graph-Based Trust Model for Evaluating Trust Using Subjective Logic

Graph-Based Trust Model for Evaluating Trust Using Subjective Logic

1..n controls 0..n Fig. 2. Graphical view of S OCIOPATH as a UML class diagram. Figure 3 presents a graphical representation of a simple system drawn by apply- ing S OCIO P ATH . Consider that a person John wants to achieve the activity “accessing the document toto using GoogleDocs ”. In the social world, the person John owns some Data , a PC and an iPad . Microsoft , Google and Apple are moral persons who provide resources and artifacts. Renater , Orange and SFR are French telco com- panies. John’s iPad is connected to SFR Servers and Renater Servers as well as John’s PC is connected to Orange Servers . On the other hand, in the digital world, the operating system Windows is running on John’s PC. Windows supports IExplorer . John’s iPad supports the running iOS , which supports the application Safari . John’s
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