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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
241

Coordination locale et optimisation distribuée du trafic de véhicules autonomes dans un réseau routier / Local coordination and distributed optimization of autonomous vehicle traffic in road networks

Tlig, Mohamed 26 March 2015 (has links)
Dans le cadre de cette thèse, nous nous intéressons à la coordination et l'optimisation du trafic aux intersections des réseaux routiers, avec la particularité de considérer des véhicules autonomes intelligents. Cette thèse est organisée en deux grandes parties. La première se concentre sur le problème du partage d'un espace de voie par deux files de véhicules évoluant en sens opposés. L'état de l'art montre le peu de travaux abordant cette question. Nous explorons deux approches par coordination réactive, en relation avec un critère de minimisation des retards. Les performances de ces approches ont été mesurées statistiquement en simulation. La deuxième partie de la thèse s'attaque au problème générique de la gestion du trafic au sein d'un réseau routier. Nous développons une approche originale à deux égards: d'une part elle explore un principe de passage en alternance des flux permettant de ne pas arrêter les véhicules aux intersections, et d'autre part, elle propose des algorithmes d'optimisationdistribuée de ce passage alterné au niveau de chaque intersection et au niveau du réseau global. La thèse présente successivement les choix de modélisation, les algorithmes et l'étude en simulation de leurs performances comparées à desapproches existantes / In this thesis, we focus on traffic coordination and optimization in road intersections, while accounting for intelligent autonomous vehicles. This thesis is organized in two parts. The first part focuses on the problem of sharing a one-lane road between two opposite flows of vehicles. The state of the art shows few studies addressing this issue. We propose two reactive coordination approaches that minimize vehicle delays and measure their performances statistically through simulations. The second part of the thesis addresses the problem of generic traffic management in a traffic network. We develop a stop-free approach that explores a principle alternating vehicles between flows at intersections, and it provides distributed algorithms optimizing this alternation at each intersection and in the overall network. We present the modeling choices, the algorithms and the simulation study of our approach and we compare its performances with existing approaches
242

[en] SIMULATION AND STOCK TRADING STRATEGIES WITH SOFTWARE AGENTS / [pt] SIMULAÇÃO E ESTRATÉGIAS DE NEGOCIAÇÃO DE AÇÕES COM AGENTES DE SOFTWARE

DIEGO BISPO CONCEICAO 12 June 2012 (has links)
[pt] O mercado financeiro tem apresentado grande crescimento na automatização de decisões e execução de estratégias que consigam atingir boas rentabilidades a partir de investimentos realizados. Conseqüentemente, a necessidade de ambientes cada vez mais robustos e confiáveis, que permitam analisar diferentes estratégias de investimentos, tem aumentado. Baseado nessa necessidade, essa dissertação apresenta o A Multi-Agent System Framework For Automated Stock Exchange Simulation (FrAMEX), framework que permite a criação de diferentes simuladores para o mercado financeiro baseado no paradigma de agentes de software. No documento são apresentados simuladores intradiário e diário criados a partir do FrAMEx, além da análise de diferentes estratégias de investimentos utilizadas em tais ambientes e executadas a partir de agentes investidores. Como diversos desses agentes alcançaram bons desempenhos em suas execuções, eles participaram de duas versões da competição MASSES, sendo dois deles os agentes campeões. Assim, a descrição de como foi o desempenho de cada agente desenvolvido também é apresentado. / [en] The financial market has presented significant growth in the automation of decisions and execution of strategies that can achieve good returns from investments. Consequently, the need for an increasingly robust and reliable environment, allowing to analyze different investment strategies, has increased. Based on this need, this work presents A Multi-Agent System Framework For Automated Stock Exchange Simulation (FrAMEX), which allows the creation of different simulators for the financial market based on the paradigm of software agents. Intraday and interday simulators created from FrAMEx are presented in the document. Besides the analysis of different investment strategies used in such environments and executed by agents run from investors. Since these agents achieved good performances in their executions, they participated in two versions of the MASSES competition. Thus, the description of the performance of each agent developed is also presented.
243

Un système multi-agents pour la gestion des connaissances hétérogènes et distribuées / Multi-agents system for heterogeneous and distributed knowledge management

Lahoud, Inaya 10 September 2013 (has links)
La gestion des connaissances permet d'identifier et de capitaliser les savoirs faires de l'entreprise afin de les organiser et de les diffuser. Cette thèse propose un système de gestion des connaissances hétérogènes et distribuées, appelé OCEAN. Basé sur les ontologies et sur un système multi-agents, OCEAN a pour but de résoudre le problème de la capitalisation et de réutilisation des connaissances provenant de plusieurs sources différentes, afin d’aider les acteurs métiers dans le processus de développement de produits mécaniques. Le système OCEAN repose sur un cycle de vie de quatre étapes Ce cycle de vie possède les phases : d’identification, d’extraction, de validation et se termine par la réutilisation des connaissances. Chaque phase constitue l’objectif d’une organisation d’agents.L’identification dans le système OCEAN consiste à définir les connaissances par un expert métier sous la forme d’une ontologie. Les ontologies sont utilisées dans notre système pour représenter les connaissances définis d’une façon structurée et formelle afin d’être compréhensible par les machines. L’extraction des connaissances dans OCEAN est réalisée par les agents de manière automatique à l’aide des ontologies créées par les experts métiers. Les agents interagissent avec les différentes applications métiers via des services web. Le résultat de cette phase est stocké dans une mémoire organisationnelle. La validation des connaissances consiste à permettre aux acteurs métiers de valider les connaissances de la mémoire organisationnelle dans un wiki sémantique. Ce wiki permet de présenter les connaissances de la mémoire organisationnelle aux acteurs pour les réutiliser, les évaluer et les faire évoluer. La réutilisation des connaissances dans OCEAN est inspiré de travaux antérieurs intégrés au sein d’OCEAN. Les quatre phases du cycle de vie des connaissances traitées dans cette thèse nous ont permis de réaliser un système apte à gérer les connaissances hétérogènes et distribuées dans une entreprise étendue. / Among the goals of Knowledge Management we can cite the identification and capitalization of the know-how of companies in order to organize and disseminate them. This thesis proposes a heterogeneous and distributed knowledge management system, called OCEAN. Based on ontologies and multi-agents system, OCEAN aims to solve the problem of capitalization and reuse of multi-sources knowledge in order to assist business actors in the development process of mechanical products. The OCEAN system is based on a knowledge life cycle composed by four steps. This knowledge life cycle begins with the identification then extraction, validation and finishes with knowledge reuse. Each step is the goal of an organization of agents.The identification in OCEAN system consists in the definition of knowledge by a business expert with an ontology. Ontologies are used in our system to represent the knowledge, defined by the business expert, in a structured and formal way in order to be understandable by machines. Agents according to the ontology defined by business experts realize knowledge extraction in OCEAN automatically. Agents interact with professional softwares via web services. The result of this extraction is stored in an organizational memory (OM). Validation of knowledge in OCEAN relies on business actors that validate the knowledge of the OM in a semantic wiki. This wiki allows also the presentation of this knowledge to business actors in order to reuse, evaluate or evolve it. Previous works, integrated within OCEAN, inspires the knowledge reuse step. The four steps lifecycle discussed in this thesis has enabled us to achieve a system that can manage heterogeneous and distributed knowledge in an extended enterprise.
244

A multi-agent based cooperative control model applied to the management of vehicles-trains / Un modèle de contrôle coopératif multi-agent appliqué à la gestion de trains de véhicules

Chen, Bofei 10 February 2017 (has links)
L'utilisation de véhicules individuels est de plus en plus importante dans les centres-villes. Ceci entraîne de nombreux effets secondaires tels que la pollution, l'embouteillage et une augmentation des accidents. Les technologies liées au développement des véhicules intelligents ont pour but de surmonter ces problèmes. Certaines des solutions proposées sont déjà accessibles au grand public, telles que les systèmes de préventions des collisions ou les aides aux maintient dans les files de circulation... Actuellement, de nombreux travaux se concentrent sur la recherche de solutions adaptées et acceptables à ces problèmes et notamment sur la gestion des embouteillages. Les solutions proposées permettent de résoudre le problème du trafic, que ce soit au niveau du système, en se concentrant sur la gestion de feux de circulation ou au niveau individuel en offrant aux véhicules de meilleurs systèmes de contrôle et de perception visant à réduire le temps de réponse et / ou à accroître la capacité des routes.Du point de vue des véhicules, l'une des solutions les plus prometteuses est de regrouper les véhicules en convoi (trains de véhicules ou platoon). Deux principales tendances peuvent être trouvées dans la littérature. D'un côté, les approches globales sont basées sur un référentiel commun, généralement lié au lieu d'évolution des véhicules, et partagé par tous les véhicules du train. Ensuite, chaque véhicule se comporte en prenant en compte cette référence partagée qui peut être soit la trajectoire du premier véhicule du train, soit une trajectoire de référence construite au préalable. La seconde catégorie dite de type approche locale est basée sur les capacités de perception locales des véhicules. Dans ce cadre, certaines méthodes, basées sur des algorithmes de contrôle classiques ou sur des liaisons d'interaction physiques et inter-véhicules, sont développées.Malgré de nombreux travaux sur ce sujet, qui se concentrent principalement sur le contrôle des véhicules individuels, peu d'entre eux considèrent le contrôle de convoi d'un point de vue système de transport. Or, ce point de vue système est particulièrement important lorsque plusieurs convoi doivent partager le réseau routier et se rencontrer à des nœuds critiques tels que carrefours et ronds-points. Cette problématique introduit de nouveaux défis tels que: 1) l'organisation des véhicules en trains de véhicules, 2) les interactions entre les trains de véhicules et 3) les stratégies de partage de l'infrastructure routière efficaces, fiables et sûres. Résoudre ces problèmes permettra alors d'envisager la solution train de véhicules comme un bon candidat pour résoudre les problèmes de flux de trafic au niveau du système de transport.Le but de cette thèse est de proposer une approche basée sur le paradigme multi-agent se focalisant sur les problématiques liées aux intersections entre des trains de véhicules. Ainsi, nous proposons un modèle de contrôle coopératif reposant sur des processus décisionnels multi-niveaux. Ce contrôle permet à la fois de préserver la cohérence et la sécurité de chaque train de véhicule et d'adapter leur comportement de manière à rendre efficace le partage de l'infrastructure. le modèle proposé est divisé en trois niveaux différents: au niveau du train, au niveau véhicule et au niveau composant de la chaîne de contrôle/commande. Cette thèse se focalise principalement sur les deux premiers niveaux. Ainsi, le processus décisionnel du train prend ses informations au niveau des autres trains et de ses constituants et envoi des requêtes au niveau véhicule. Le processus décisionnel au niveau véhicule fusionne les informations locales de sa perception propre et celles fournies par le train et produit des consignes appliquées par le niveau contrôle/commande. Cette thèse étudie également les possibilités de reconfiguration dynamique des trains en utilisant les intersections. / The use of individual vehicles is becoming more and more important in inner cities, leading to many side problems such as traffic jam, air pollution and accidents. Intelligent vehicles have been studied so as to overcome these problems. Some solutions provided by these works are already available to the general public market such as city safety systems, lane assists,... Many research works are focusing on finding suitable and acceptable solutions to these problems and dealing with traffic jam management. The proposal can tackle the traffic jam problem whether on system level or on individual vehicle providing better control and perception systems aimed at reducing time response and/or at increasing the road capacity.On the vehicle side, one promising solutions is vehicles platoons (vehicles-train) making possible a huge reduction of the longitudinal distance between vehicles and thus allowing an increase of roads capacity. Basically, two main trends can be found literature. On one side, global approaches are based on a common reference frame, generally tied to the vehicles playground, shared by all vehicles of the train. Then, each vehicle behaves according to this shared reference which can be either the trajectory of the first vehicle of the train or a reference trajectory built offline. On the other side, local approaches are based on vehicle local perception abilities. Some methods, based on classical control algorithms or physical-inspired and inter-vehicular interaction link, are developed.Despite numerous research works on this subject, which are focusing on individual vehicle control, few of them consider the platoon control solution on the system point of view. However, this system point of view is particularly important when several platoons have to share the road network and meet at critical nodes such as crossroads and roundabouts. This introduces new issues such as (1) how to organize vehicles and trains of vehicle, (2) the interactions between trains of vehicles and (3) the strategies of sharing the road infrastructure efficient, reliable and safe. Solving these problems will then allow considering vehicles-train solution as a good candidate for solving traffic flow issues at transportation system level.The goal of this thesis is to propose an approach, based on multi-agent paradigm, which aims at dealing with systems level issues focusing mainly on intersections between vehicles-trains of vehicles. Thus, we propose a cooperative control system which relies on multi-level decision processes aimed at dealing with the interaction of platoons at road network nodes. This cooperative control system allows both to maintain the coherence and the safety condition of each involved train of vehicles and to adapt each train components behavior so as to make train shared the road, and especially roundabouts and crossroads, efficiently (i.e. without stopping any vehicle). This cooperative control system is divided into three different levels. The global train state is managed at the train-level decision process based on the train level perceptions. The vehicle-level process makes the decision concerning each individual vehicle according to data provided by the train-level and to the interaction between vehicles. Finally, the motor-level process makes the link between the vehicle-level command and hardware level of vehicles. In this thesis, we focus on the train-level and vehicle-level. When encountering, trains exchange information such as one part of their perceptions.Besides the goal of having an efficient approach so as to enable several vehicles-trains to share the road infrastructure, we also strategies to transform the meetings of vehicles-trains at road nodes into reconfiguration spots where trains can reconfigure and recombine.The developed algorithm are tested in simulation so as to obtain proper evaluation of our proposal using suitable indicators.
245

[en] AN ASPECT-ORIENTED FRAMEWORK FOR SOFTWARE AGENTS MOBILITY / [pt] UM FRAMEWORK ORIENTADO A ASPECTOS PARA MOBILIDADE DE AGENTES DE SOFTWARE

CIDIANE ARACATY LOBATO 29 March 2006 (has links)
[pt] Engenheiros de sistemas multi-agentes (SMAs) móveis devem lidar com o projeto e a implementação de mobilidade de código, além do projeto e implementação de funcionalidades básicas e outros requisitos. À medida que a complexidade dos SMAs aumenta, questões referentes à mobilidade não podem ser modularizadas somente a partir da utilização de abstrações e mecanismos orientados a objetos (OO). Além disso, vários programadores freqüentemente evidenciam a presença de problemas de entrelaçamento e espalhamento em suas linhas de código referentes à mobilidade. Apesar de tais problemas, os desenvolvedores de SMAs têm se apoiado vastamente na utilização de interfaces de programação de aplicações (APIs) OO das plataformas de mobilidade e na linguagem de programação Java. O resultado é a produção de SMAs que são difíceis de entender, manter e reutilizar. Este trabalho apresenta três contribuições principais. Primeiramente, é realizada uma análise das soluções existentes para separação dos interesses de mobilidade. Além disso, são propostos a arquitetura de software ArchM e o framework AspectM, ambos baseados em aspectos, visando: (i) uma clara separação dos interesses de mobilidade em relação às funcionalidades básicas e outros requisitos, (ii) uma introdução transparente do código de mobilidade em agentes estacionários, e (iii) uma integração flexível dos SMAs com plataformas de mobilidade existentes. O desenvolvimento de software orientado a aspectos é um novo paradigma com abstrações e mecanismos de composição que possibilitam o aumento do grau de reusabilidade e manutenibilidade dos sistemas. Os benefícios de ArchM e AspectM são ilustrados através de dois estudos de caso e com o uso de duas plataformas de mobilidade. / [en] Software engineers of multi-agent systems (MASs) are concerned with the design and implementation of the mobility issues in addition to the agents` basic functionalities and other agent-related concerns. As the agents` complexity increases, mobility issues cannot be modularized based only on object-oriented (OO) abstractions and mechanisms. Besides, some programmers frequently evidence the presence of mobility tangling and scattering problems on their systems. Despite these problems, MAS developers have mostly relied on application programming interfaces (APIs) OO from mobility platforms and on the use of the Java programming language. The result is the production of MASs that are difficult to understand, maintain, and reuse. This work presents three main contributions. Firstly, an analysis of existent solutions for modularization of mobility issues. Besides, the proposal of the ArchM software architecture and the AspectM framework, both based on aspects, which support: (i) improved modularization of the mobility issues, that is, a clean separation between the mobility-specific concerns and the other agent concerns, (ii) a seamless introduction of code mobility into stationary agents, and (iii) a flexible integration with multiple mobility platforms. The aspect- oriented software development (AOSD) is a new paradigm with abstractions and composition mechanisms that support an improvement of reuse and maintainability of systems. The benefits of the AspectM framework are illustrated through two case studies and through use of two mobility platforms.
246

Tisser le Web Social des Objets : Permettre une Interaction Autonome et Flexible dans l’Internet des Objets / Weaving a Social Web of Things : Enabling Autonomous and Flexible Interaction in the Internet of Things

Ciortea, Andrei-Nicolae 14 January 2016 (has links)
L’Internet des Objets (IoT) vise à créer un eco-système global et ubiquitaire composé d’un grand nombre d’objets hétérogènes. Afin d’atteindre cette vision, le World Wide Web apparaît comme un candidat adapté pour interconnecter objets et services à la couche applicative en un Web des Objets (WoT).Cependant l’évolution actuelle du WoT produit des silos d’objets et empêche ainsi la mise en place de cette vision. De plus, même si le Web facilite la composition d’objets et services hétérogènes, les approches existantes produisent des compositions statiques incapables de s’adapter à des environnements dynamiques et des exigences évolutives. Un autre défi est à relever: permettre aux personnes d’interagir avec le vaste, évolutif et hétérogène IoT.Afin de répondre à ces limitations, nous proposons une architecture pour IoT ouvert et autogouverné, constitué de personnes et d’objets situés, en interaction avec un environnement global via des plateformes hétérogènes. Notre approche consiste de rendre les objets autonomes et d’appliquer la métaphore des réseaux sociaux afin de créer des réseaux flexibles de personnes et d’objets. Nous fondons notre approche sur les résultats issus des domaines des multi-agents et du WoT afin de produit un WoT Social.Notre proposition prend en compte les besoins d’hétérogénéité, de découverte et d’interaction flexible dans l’IoT. Elle offre également un coût minimal pour les développeurs et les utilisateurs via différentes couches d’abstraction permettant de limité la complexité de cet éco-système. Nous démontrons ces caractéristiques par la mise en oeuvre de plus scénarios applicatifs. / The Internet of Things (IoT) aims to create a global ubiquitous ecosystem composed of large numbers of heterogeneous devices. To achieve this vision, the World Wide Web is emerging as a suitable candidate to interconnect IoT devices and services at the application layer into a Web of Things (WoT).However, the WoT is evolving towards large silos of things, and thus the vision of a global ubiquitous ecosystem is not fully achieved. Furthermore, even if the WoT facilitates mashing up heterogeneous IoT devices and services, existing approaches result in static IoT mashups that cannot adapt to dynamic environments and evolving user requirements. The latter emphasizes another well-recognized challenge in the IoT, that is enabling people to interact with a vast, evolving, and heterogeneous IoT.To address the above limitations, we propose an architecture for an open and self-governed IoT ecosystem composed of people and things situated and interacting in a global environment sustained by heterogeneous platforms. Our approach is to endow things with autonomy and apply the social network metaphor to createflexible networks of people and autonomous things. We base our approach on results from multi-agent and WoT research, and we call the envisioned IoT ecosystem the Social Web of Things.Our proposal emphasizes heterogeneity, discoverability and flexible interaction in the IoT. In the same time, it provides a low entry-barrier for developers and users via multiple layers of abstraction that enable them to effectively cope with the complexity of the overall ecosystem. We implement several application scenarios to demonstrate these features.
247

Tisser le Web Social des Objets : Permettre une Interaction Autonome et Flexible dans l’Internet des Objets / Weaving a Social Web of Things : Enabling Autonomous and Flexible Interaction in the Internet of Things

Ciortea, Andrei-Nicolae 14 January 2016 (has links)
L’Internet des Objets (IoT) vise à créer un eco-système global et ubiquitaire composé d’un grand nombre d’objets hétérogènes. Afin d’atteindre cette vision, le World Wide Web apparaît comme un candidat adapté pour interconnecter objets et services à la couche applicative en un Web des Objets (WoT).Cependant l’évolution actuelle du WoT produit des silos d’objets et empêche ainsi la mise en place de cette vision. De plus, même si le Web facilite la composition d’objets et services hétérogènes, les approches existantes produisent des compositions statiques incapables de s’adapter à des environnements dynamiques et des exigences évolutives. Un autre défi est à relever: permettre aux personnes d’interagir avec le vaste, évolutif et hétérogène IoT.Afin de répondre à ces limitations, nous proposons une architecture pour IoT ouvert et autogouverné, constitué de personnes et d’objets situés, en interaction avec un environnement global via des plateformes hétérogènes. Notre approche consiste de rendre les objets autonomes et d’appliquer la métaphore des réseaux sociaux afin de créer des réseaux flexibles de personnes et d’objets. Nous fondons notre approche sur les résultats issus des domaines des multi-agents et du WoT afin de produit un WoT Social.Notre proposition prend en compte les besoins d’hétérogénéité, de découverte et d’interaction flexible dans l’IoT. Elle offre également un coût minimal pour les développeurs et les utilisateurs via différentes couches d’abstraction permettant de limité la complexité de cet éco-système. Nous démontrons ces caractéristiques par la mise en oeuvre de plus scénarios applicatifs. / The Internet of Things (IoT) aims to create a global ubiquitous ecosystem composed of large numbers of heterogeneous devices. To achieve this vision, the World Wide Web is emerging as a suitable candidate to interconnect IoT devices and services at the application layer into a Web of Things (WoT).However, the WoT is evolving towards large silos of things, and thus the vision of a global ubiquitous ecosystem is not fully achieved. Furthermore, even if the WoT facilitates mashing up heterogeneous IoT devices and services, existing approaches result in static IoT mashups that cannot adapt to dynamic environments and evolving user requirements. The latter emphasizes another well-recognized challenge in the IoT, that is enabling people to interact with a vast, evolving, and heterogeneous IoT.To address the above limitations, we propose an architecture for an open and self-governed IoT ecosystem composed of people and things situated and interacting in a global environment sustained by heterogeneous platforms. Our approach is to endow things with autonomy and apply the social network metaphor to createflexible networks of people and autonomous things. We base our approach on results from multi-agent and WoT research, and we call the envisioned IoT ecosystem the Social Web of Things.Our proposal emphasizes heterogeneity, discoverability and flexible interaction in the IoT. In the same time, it provides a low entry-barrier for developers and users via multiple layers of abstraction that enable them to effectively cope with the complexity of the overall ecosystem. We implement several application scenarios to demonstrate these features.
248

Definición de un modelo de gestión de las nociones de confianza y reputación entre agentes. Enfoque basado en la similitud entre tareas.

Caballero Martínez, Alberto 04 April 2008 (has links)
Los conceptos de confianza y reputación determinan un campo de investigación relevante para varias disciplinas científicas. Desde el punto de vista de las Ciencias de la Computación, una gran parte de los esfuerzos en esta dirección se ha dedicado a la definición de mecanismos de control adaptativos de las comunidades virtuales tomando como referencia las relaciones que se presentan en las sociedades humanas. El hecho de tener en cuenta elementos asociados a la confianza y la reputación contrarresta el elevado grado de incertidumbre bajo el cual los individuos toman sus decisiones. Así, un modelo de confianza y reputación hace frente a la incertidumbre asociada a las decisiones que toman las partes "inteligentes" de varios tipos de sistemas. En este sentido, resulta importante proporcionar algunos mecanismos de estimación de los valores de confianza y reputación que permitan ofrecer recomendaciones valiosas aun cuando no se disponga de la información suficie nte para hacerlo. También destaca la necesidad de adopción de algún modelo conceptual común y eficaz para la representación de los elementos dependientes del dominio de aplicación.Esta tesis está dedicada a la definición y estudio de un modelo de confianza y reputación que, adoptando un marco de representación ontológica para la definición de los elementos dependientes del dominio de aplicación, utiliza criterios de similitud para estimar el desempeño de las partes del sistema cuando la información relacionada se presenta incompleta. Se estudia el comportamiento del modelo para diferentes alternativas de definición de algunos de sus elementos, y frente a diferentes situaciones experimentales, determinadas por las variaciones del desempeño de los elementos del sistema. / . The concepts of trust and reputation determine an important research field for several scientific disciplines. From the point of view of Computer Sciences, a large amount of efforts in this direction has been devoted to the definition of adaptive control mechanisms for virtual communities based on the relationships that take place in human societies. Taking into account some elements associated with trust and reputation, the high degree of uncertainty, under which individuals make decisions, is reduced. Thus, a trust and reputation model could help to deal with the uncertainty associated with the decisions of "smart" parties, in some types of systems.This way, it is important to provide some mechanism to estimate the trust and reputation values in order to give valuable recommendations, even if there are no sufficient information to do so. It also stands out the necessity to adopt a common and effective conceptual model for the representation of the application doma in elements.This thesis is devoted to the definition and study of a trust and reputation model, based on a common ontological framework for the definition of domain-dependent elements, using similarity criteria for estimating the performance of parts of the system when related information is incomplete. Also it analyzes the behavior of the model to different alternatives for the definition of some of its elements, and in front of different experimental situations, determined by variations in the performance of the system elements.
249

Constrained Rationality: Formal Value-Driven Enterprise Knowledge Management Modelling and Analysis Framework for Strategic Business, Technology and Public Policy Decision Making & Conflict Resolution

Al-Shawa, Mohammed Majed 19 May 2011 (has links)
The complexity of the strategic decision making environments, in which busi- nesses and governments live in, makes such decisions more and more difficult to make. People and organizations with access to the best known decision support modelling and analysis tools and methods cannot seem to benefit from such re- sources. We argue that the reason behind the failure of most current decision and game theoretic methods is that these methods are made to deal with operational and tactical decisions, not strategic decisions. While operational and tactical decisions are clear and concise with limited scope and short-term implications, allowing them to be easily formalized and reasoned about, strategic decisions tend to be more gen- eral, ill-structured, complex, with broader scope and long-term implications. This research work starts with a review of the current dominant modelling and analysis approaches, their strengths and shortcomings, and a look at how pioneers in the field criticize these approaches as restrictive and unpractical. Then, the work goes on to propose a new paradigm shift in how strategic decisions and conflicts should be modelled and analyzed. Constrained Rationality is a formal qualitative framework, with a robust method- ological approach, to model and analyze ill-structured strategic single and multi- agent decision making situations and conflicts. The framework brings back the strategic decision making problem to its roots, from being an optimization/efficiency problem about evaluating predetermined alternatives to satisfy predetermined pref- erences or utility functions, as most current decision and game theoretic approaches treats it, to being an effectiveness problem of: 1) identifying and modelling explic- itly the strategic and conflicting goals of the involved agents (also called players and decision makers in our work), and the decision making context (the external and internal constraints including the agents priorities, emotions and attitudes); 2) finding, uncovering and/or creating the right set of alternatives to consider; and then 3) reasoning about the ability of each of these alternatives to satisfy the stated strategic goals the agents have, given their constraints. Instead of assuming that the agents’ alternatives and preferences are well-known, as most current decision and game theoretic approaches do, the Constrained Rationality framework start by capturing and modelling clearly the context of the strategic decision making situation, and then use this contextual knowledge to guide the process of finding the agents’ alternatives, analyzing them, and choosing the most effective one. The Constrained Rationality framework, at its heart, provides a novel set of modelling facilities to capture the contextual knowledge of the decision making sit- uations. These modelling facilities are based on the Viewpoint-based Value-Driven - Enterprise Knowledge Management (ViVD-EKM) conceptual modelling frame- work proposed by Al-Shawa (2006b), and include facilities: to capture and model the goals and constraints of the different involved agents, in the decision making situation, in complex graphs within viewpoint models; and to model the complex cause-effect interrelationships among theses goals and constraints. The framework provides a set of robust, extensible and formal Goal-to-Goal and Constraint-to Goal relationships, through which qualitative linguistic value labels about the goals’ op- erationalization, achievement and prevention propagate these relationships until they are finalized to reflect the state of the goals’ achievement at any single point of time during the situation. The framework provides also sufficient, but extensible, representation facilities to model the agents’ priorities, emotional valences and attitudes as value properties with qualitative linguistic value labels. All of these goals and constraints, and the value labels of their respective value properties (operationalization, achievement, prevention, importance, emotional valence, etc.) are used to evaluate the different alternatives (options, plans, products, product/design features, etc.) agents have, and generate cardinal and ordinal preferences for the agents over their respective alternatives. For analysts, and decision makers alike, these preferences can easily be verified, validates and traced back to how much each of these alternatives con- tribute to each agent’s strategic goals, given his constraints, priorities, emotions and attitudes. The Constrained Rationality framework offers a detailed process to model and analyze decision making situations, with special paths and steps to satisfy the spe- cific needs of: 1) single-agent decision making situations, or multi-agent situations in which agents act in an individualistic manner with no regard to others’ current or future options and decisions; 2) collaborative multi-agent decision making situ- ations, where agents disclose their goals and constraints, and choose from a set of shared alternatives one that best satisfy the collective goals of the group; and 3) adversarial competitive multi-agent decision making situations (called Games, in gamete theory literature, or Conflicts, in the broader management science litera- ture). The framework’s modelling and analysis process covers also three types of con- flicts/games: a) non-cooperative games, where agents can take unilateral moves among the game’s states; b) cooperative games, with no coalitions allowed, where agents still act individually (not as groups/coalitions) taking both unilateral moves and cooperative single-step moves when it benefit them; and c) cooperative games, with coalitions allowed, where the games include, in addition to individual agents, agents who are grouped in formal alliances/coalitions, giving themselves the ability to take multi-step group moves to advance their collective position in the game. ....
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Graph-Based Control of Networked Systems

Ji, Meng 11 June 2007 (has links)
Networked systems have attracted great interests from the control society during the last decade. Several issues rising from the recent research are addressed in this dissertation. Connectedness is one of the important conditions that enable distributed coordination in a networked system. Nonetheless, it has been assumed in most implementations, especially in continuous-time applications, until recently. A nonlinear weighting strategy is proposed in this dissertation to solve the connectedness preserving problem. Both rendezvous and formation problem are addressed in the context of homogeneous network. Controllability of heterogeneous networks is another issue which has been long omitted. This dissertation contributes a graph theoretical interpretation of controllability. Distributed sensor networks make up another important class of networked systems. A novel estimation strategy is proposed in this dissertation. The observability problem is raised in the context of our proposed distributed estimation strategy, and a graph theoretical interpretation is derived as well. The contributions of this dissertation are as follows: It solves the connectedness preserving problem for networked systems. Based on that, a formation process is proposed. For heterogeneous networks, the leader-follower structure is studied and sufficient and necessary conditions are presented for the system to be controllable. A novel estimation strategy is proposed for distributed sensor networks, which could improve the performance. The observability problem is studied for this estimation strategy and a necessary condition is obtained. This work is among the first ones that provide graph theoretical interpretations of the controllability and observability issues.

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