Trust Management within Virtual Communities: Adaptive and Socially-Compliant Trust Model

21 pagesRecent years have witnessed increasing interest of people in sharing, collaborating and interacting in many different ways among new social structures called Virtual Communities (VC). They represent aggrega- tions of entities with common interests, goals, practices or values. VCs are particularly complex environments wherein trust became, rapidly, a prerequisite for the decision-making process, and where traditional trust establishment techniques are regularly challenged. In our work we are considering how individual and collective trust policies can be managed, adapted and combined. To this aim, we propose an Adaptive and Socially-Compliant Trust Management System (ASC-TMS) based on multi-agent technologies. In this framework, policies are used as concrete implementations of trust models in order to specify both (i) user-centred (i.e. personal) and community-centred (i.e. collective) trust requirements. Agents are used to manage and combine these different policies in a decentralized and flexible way. We describe the functionalities and the architecture that supports them and discuss also a prototype implementation

Gestion de la confiance et intégration des exigences sociales au sein de communautés virtuelles

http://www.emse.fr/~picard/publications/yaich11jfsma.pdfInternational audienceLa confiance est devenue un facteur clé des processus de décision au sein de communautés virtuelles. Le caractère ouvert et décentralisé de ces environnements couplés à leur dimension sociale défient les mécanismes actuelles de gestion de la confiance. Notamment pour ce qui concerne la gestion et l'intégration des exigences de confiance des utilisateurs et ceux de leurs communautés. Afin de répondre à ce problème, nous proposons SC-TMS, un système de gestion de la confiance adaptatif basé sur le principe de conformité sociale [4]. En nous appuyant sur les technologies multi-agents, des politiques de confiance sont utilisées pour spécifier à la fois les modèles de confiance centrés utilisateur et les modèles centrés communauté. Les agents y sont utilisés pour gérer et combiner ces différentes politiques de manière flexible et décentralisée. Nous décrivons les fonctionnalités et l'architecture qui les mettent en oeuvre et discutons de leur implémentation

Using Metadata to Improve Organization and Information Retrieval on the WWW

http://www.emse.fr/~beigbeder/PUBLIS/1998-webnet-pXXX-doan.pdfInternational audience: Until now the growing volume of heterogeneous and distributed information on the WWW makes increasingly difficult for the existing tools to retrieve relevant information. To improve the performance of these tools, we suggest to handle two aspects of the problem: One concerns a better representation and description of WWW pages, we introduce here a new concept of "WWW documents", and we describe them thanks to metadata. We'll use the Dublin Core semantics and the XML syntax to represent these metadata. We'll suggest how this concept can improve information retrieval on the WWW and reduce the network load generated by robots. Then, we describe a flexible architecture based on two kinds of robots : "generalists" and "specialists" that collect and organize these metadata, in order to localize the resources on the WWW. They will contribute to the overall auto-organizing information process by exchanging their indices

Persistent transient myocardial ischemia despite beta-adrenergic blockade predicts a higher risk of adverse cardiac events in patients with coronary artery disease

AbstractObjectives. We evaluated the prevalence and prognostic significance of transient myocardial ischemia despite beta-adrenergic blockade in patients with coronary artery disease.Background. Persistence of transient ischemia despite therapy may correspond to a subset of high risk patients with coronary disease. The impact of beta-blocker withdrawal in these patients remains unknown.Methods. Patients (n = 313) with documented coronary artery disease and beta-blocker therapy, with (group I, n = 84) or without (group II, n = 229) transient ischemia on ambulatory electrocardiographic monitoring, were followed up during 21 ± 9 months for cardiac events (death, myocardial infarction, percutaneous transluminal coronary angioplasty, coronary artery bypass surgery and worsening angina). Occurrence of events was compared by log-rank test.Results. The number of coronary stenoses did not differ significantly between groups I and II. Beta-blocker therapy was discontinued more frequently during follow-up in group II (25% vs. 14% in group I, p = 0.04). Cumulative percentage of death or myocardial infarction, or both, tended to be higher in group I at 30 months (17% vs. 5% in group II, p = 0.09). Coronary angioplasty and bypass surgery were significantly more frequent in group I (p = 0.01 and 0.0008, respectively). Transient ischemia was associated with a higher cumulative probability of adverse events (p = 0.004). The number of coronary stenoses, presence of transient ischemia and beta-blocker withdrawal were the only significant prognostic factors of cardiac events in the Cox model. In group I patients, the relative hazard of cardiac events was increased threefold when beta-blocker therapy was interrupted.Conclusions. These data suggest that 1) the occurrence of transient ischemia despite beta-blocker therapy identifies a subset of high risk patients with coronary artery disease, and 2) the interruption of beta-blocker therapy increases the risk of adverse cardiac events

DREW : Un outil Internet pour créer des situations d'apprentissage coopérant

http://archiveseiah.univ-lemans.fr/EIAH2003/Pdf_annexes/Corbel.pdfNational audienceDREW1 (Dialogical Reasoning Educational Web tool) est un environnement informatisé d'apprentissage humain collaboratif, développé en Java. Cet environnement est développé dans le cadre du projet européen SCALE2 (IST-1999) dont l'objectif pédagogique est de favoriser un apprentissage collaboratif basé sur l'argumentation (CABLE). En d'autres mots, l'objectif est d'amener les élèves du secondaire à " apprendre à travers des activités argumentatives ". Pour cela, à partir de l'environnement d'apprentissage DREW, différentes séquences d'enseignement et outils ont été conçus pour aider les élèves à acquérir, raffiner et étendre leur connaissance argumentative dans un domaine donné (le débat sur les OGM). Dans ce papier, nous nous limitons à présenter l'interface des outils élève (outils de communication et construction collaborative) et l'interface enseignant/chercheur proposées dans l'environnement (rejoueur d'interaction et outil de conception de tâches), puis les caractéristiques du système. Nous donnerons quelques propositions d'utilisation de ces outils dans le cadre d'activités pédagogiques

Genome sequence of the stramenopile Blastocystis, a human anaerobic parasite

International audienceABSTRACT: BACKGROUND: Blastocystis is a highly prevalent anaerobic eukaryotic parasite of humans and animals that is associated with various gastrointestinal and extraintestinal disorders. Epidemiological studies have identified different subtypes but no one subtype has been definitively correlated with disease. RESULTS: Here we report the 18.8 Mb genome sequence of a Blastocystis subtype 7 isolate, which is the smallest stramenopile genome sequenced to date. The genome is highly compact and contains intriguing rearrangements. Comparisons with other available stramenopile genomes (plant pathogenic oomycete and diatom genomes) revealed effector proteins potentially involved in the adaptation to the intestinal environment, which were likely acquired via horizontal gene transfer. Moreover, Blastocystis living in anaerobic conditions harbors mitochondria-like organelles. An incomplete oxidative phosphorylation chain, a partial Krebs cycle, amino acid and fatty acid metabolisms and an iron-sulfur cluster assembly are all predicted to occur in these organelles. Predicted secretory proteins possess putative activities that may alter host physiology, such as proteases, protease-inhibitors, immunophilins and glycosyltransferases. This parasite also possesses the enzymatic machinery to tolerate oxidative bursts resulting from its own metabolism or induced by the host immune system. CONCLUSIONS: This study provides insights into the genome architecture of this unusual stramenopile. It also proposes candidate genes with which to study the physiopathology of this parasite and thus may lead to further investigations into Blastocystis-host interactions

Genetic diversity, linkage disequilibrium and power of a large grapevine (Vitis vinifera L) diversity panel newly designed for association studies

UMR-AGAP Equipe DAVV (Diversité, adaptation et amélioration de la vigne) ; équipe ID (Intégration de Données)International audienceAbstractBackgroundAs for many crops, new high-quality grapevine varieties requiring less pesticide and adapted to climate change are needed. In perennial species, breeding is a long process which can be speeded up by gaining knowledge about quantitative trait loci linked to agronomic traits variation. However, due to the long juvenile period of these species, establishing numerous highly recombinant populations for high resolution mapping is both costly and time-consuming. Genome wide association studies in germplasm panels is an alternative method of choice, since it allows identifying the main quantitative trait loci with high resolution by exploiting past recombination events between cultivars. Such studies require adequate panel design to represent most of the available genetic and phenotypic diversity. Assessing linkage disequilibrium extent and panel power is also needed to determine the marker density required for association studies.ResultsStarting from the largest grapevine collection worldwide maintained in Vassal (France), we designed a diversity panel of 279 cultivars with limited relatedness, reflecting the low structuration in three genetic pools resulting from different uses (table vs wine) and geographical origin (East vs West), and including the major founders of modern cultivars. With 20 simple sequence repeat markers and five quantitative traits, we showed that our panel adequately captured most of the genetic and phenotypic diversity existing within the entire Vassal collection. To assess linkage disequilibrium extent and panel power, we genotyped single nucleotide polymorphisms: 372 over four genomic regions and 129 distributed over the whole genome. Linkage disequilibrium, measured by correlation corrected for kinship, reached 0.2 for a physical distance between 9 and 458 Kb depending on genetic pool and genomic region, with varying size of linkage disequilibrium blocks. This panel achieved reasonable power to detect associations between traits with high broad-sense heritability (> 0.7) and causal loci with intermediate allelic frequency and strong effect (explaining > 10 % of total variance).ConclusionsOur association panel constitutes a new, highly valuable resource for genetic association studies in grapevine, and deserves dissemination to diverse field and greenhouse trials to gain more insight into the genetic control of many agronomic traits and their interaction with the environment

Proposition d'une arithmétique rationnelle paresseuse et d'un outil d'aide à la saisie d'objets en synthèse d'images

The most common solution to solve imprecision problems introduced by the arithmetic of computers is to use exact arithmetic. In the first part of this thesis, we suggest an extremely efficient optimization of rational arithmetic : the lazy rational arithmetic. The originality of this arithmetic is to postpone exact computations until they are either useless or inevitable. In that way, unnecessary exact computations are never made. Lazy arithmetic is an autonomous library which solves imprecision problems by itself, independently of computer programs using it. The second part of this thesis describes a modelling tool using photographs of objects to model them in a constructive solid geometry description. It is an interactive tool with which the user may build what he needs with the most adapted detail level for his own application. Proposed extensions for image synthesis may be used to solve image incrustation consistently with shadows, lights and environment reflections.La solution la plus commune pour résoudre les problèmes de précision liés aux arithmétiques des ordinateurs est l'utilisation d'arithmétiques exactes. Nous proposons dans la première partie de cette thèse une optimisation très puissante des arithmétiques rationnelles : l'arithmétique rationnelle paresseuse. L'originalité de cette arithmétique est de retarder les calculs exacts jusqu'à ce qu'ils deviennent soit inutiles, soit inévitables. Ainsi les calculs exacts qui ne sont pas nécessaires ne sont jamais faits. L'arithmétique paresseuse se présente sous la forme d'une bibliothèque autonome prenant à sa charge les problèmes de précision et qui est indépendante des programmes qui l'utilisent. La deuxième partie de cette thèse présente un outil de modélisation dont le principal intérêt est d'utiliser l'image des objets comme support à leur modélisation sous forme d'arbre de construction. Cet outil est interactif, l'utilisateur pourra de cette manière ne modéliser que ce dont il a besoin et avec le niveau de détails le plus adapté à ses applications. Les extensions que nous proposons dans le domaine de l'incrustation d'images de synthèse dans des images naturelles permettent de traiter correctement l'ombrage de la scène finale en tenant compte de la nature des éclairages, des ombres portées et des reflets

Canaux cachés en pleine lumière ou comment la lumière illuminant une fibre optique pourrait permettre de retrouver les clefs de chiffrement des communication

International audienceLes infrastructures de réseaux optiques sont aujourd’hui massivement déployées sur notre territoire. Parmi les différentes technologies disponibles, le GPON (Gigabit Passive Optical Network) est sans doute le plus répandu.Lorsque l’on s’intéresse à la sécurité des échanges sur ce type de réseau, on se rend compte que si des précautions ont bien été prises au niveau protocolaire, il serait possible, en observant la lumière illuminant les fibres optiques d’en extraire des informations qui pourraient permettre de retrouver les clefs chiffrant les communications.Cet exposé présentera de quelle manière il est possible de tirer profit du protocole ITU-G.984, les difficultés rencontrées dans le cas d’une de nos études et les résultats obtenus

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