Annotierte interaktive nichtlineare Videos - Software Suite, Download- und Cache-Management

Modern Web technology makes the dream of fully interactive and enriched video come true. Nowadays it is possible to organize videos in a non-linear way playing in a sequence unknown in advance. Furthermore, additional information can be added to the video, ranging from short descriptions to animated images and further videos. This affords an easy and efficient to use authoring tool which is capable of the management of the single media objects, as well as a clear arrangement of the links between the parts. Tools of this kind can be found rarely and do mostly not provide the full range of needed functions. While providing an interactive experience to the viewer in the Web player, parallel plot sequences and additional information lead to an increased download volume. This may cause pauses during playback while elements have to be downloaded which are displayed with the video. A good quality of experience for these videos with small waiting times and a playback without interruptions is desired. This work presents the SIVA Suite to create the previously described annotated interactive non-linear videos. We propose a video model for interactivity, non-linearity, and annotations, which is implemented in an XML format, an authoring tool, and a player. Video is the main medium, whereby different scenes are linked to a scene graph. Time controlled additional content called annotations, like text, images, audio files, or videos, is added to the scenes. The user is able to navigate in the scene graph by selecting a button at a button panel. Furthermore, other navigational elements like a table of contents or a keyword search are provided. Besides the SIVA Suite, this thesis presents algorithms and strategies for download and cache management to provide a good quality of experience while watching the annotated interactive non-linear videos. Therefor, we implemented a standard-independent player framework. Integrated into a simulation environment, the framework allows to evaluate algorithms and strategies for the calculation of start-up times, and the selection of elements to pre-fetch into and delete from the cache. Their interaction during the playback of non-linear video contents can be analyzed. The algorithms and strategies can be used to minimize interruptions in the video flow after user interactions. Our extensive evaluation showed that our techniques result in faster start-up times and lesser interruptions in the video flow than those of other players. Knowledge of the structure of an interactive non-linear video can be used to minimize the start-up time at the beginning of a video while minimizing an increase in the overall download volume.Moderne Web-Technologien lassen den Traum von voll interaktiven und bereicherten Videos wahr werden. Heutzutage ist es möglich, Videos in nicht-linearer Art und Weise zu organisieren, welche dann in einer vorher unbekannten Reihenfolge abgespielt werden können. Weiterhin können den Videos Zusatzinformationen in Form von kurzen Beschreibungen über animierte Bilder bis hin zu weiteren Videos hinzugefügt werden. Dies erfordert ein einfach und effizient zu bedienendes Autorenwerkzeug, das in der Lage ist, sowohl einzelne Medien-Objekte zu verwalten, als auch die Verbindungen zwischen den einzelnen Teilen klar darzustellen. Tools dieser Art sind selten und bieten meist nicht den vollen benötigten Funktionsumfang. Während dem Betrachter dieses interaktive Erlebnis im Web Player zur Verfügung gestellt wird, führen parallele Handlungsstränge und zusätzliche Inhalte zu einem erhöhten Download-Volumen. Dies kann zu Pausen während der Wiedergabe führen, in denen Elemente vom Server geladen werden müssen, welche mit dem Video angezeigt werden sollen. Ein gutes Benutzungserlebnis für solche Videos kann durch geringe Wartezeiten und eine unterbrechungsfreie Wiedergabe erreicht werden. Diese Arbeit stellt die SIVA Suite vor, mit der die zuvor beschriebenen annotierten interaktiven nicht-linearen Videos erstellt werden können. Wir bilden Interaktivität, Nichtlinearität und Annotationen in einem Video-Model ab. Dieses wird in unserem XML-Format, Autorentool und Player umgesetzt. Als Leitmedium werden hierbei Videos verwendet, welche aufgeteilt in Szenen zu einer Graphstruktur zusammengefügt werden können. Zeitlich gesteuerte zusätzliche Inhalte, sogenannte Annotationen, wie Texte, Bilder, Audio-Dateien und Videos, werden den Szenen hinzugefügt. Der Betrachter kann im Szenengraph navigieren, indem er in einem bereitgestellten Button-Panel eine Nachfolgeszene auswählt. Andere Navigationselemente sind ein Inhaltsverzeichnis sowie eine Suchfunktion. Neben der SIVA Suite beschreibt diese Arbeit Algorithmen und Strategien für Download und Cache Management, um eine gute Nutzungserfahrung während der Betrachtung der annotierten interaktiven nicht-linearen Videos zu bieten. Ein Webstandard-unabhängiges Playerframework erlaubt es, das Zusammenspiel von Algorithmen und Strategien zu evaluieren, welche für die Berechnung der Start-Zeitpunkte für die Wiedergabe, sowie die Auswahl von vorauszuladenden sowie zu löschenden Elemente verwendet werden. Ziel ist es, Unterbrechungen zu minimieren, wenn der Ablauf des Videos durch Benutzerinteraktion beeinflusst wird. Unsere umfassende Evaluation zeigte, dass es möglich ist, kürzere Startup-Zeiten und weniger Unterbrechungen mit unseren Strategien zu erreichen, als bei der Verwendung der Strategien anderer Player. Die Kenntnis der Struktur des interaktiven nicht-linearen Videos kann dazu verwendet werden, die Startzeit am Anfang der Szenen zu minimieren, während das Download-Volumen nicht erhöht wird

MediaSync: Handbook on Multimedia Synchronization

This book provides an approachable overview of the most recent advances in the fascinating field of media synchronization (mediasync), gathering contributions from the most representative and influential experts. Understanding the challenges of this field in the current multi-sensory, multi-device, and multi-protocol world is not an easy task. The book revisits the foundations of mediasync, including theoretical frameworks and models, highlights ongoing research efforts, like hybrid broadband broadcast (HBB) delivery and users' perception modeling (i.e., Quality of Experience or QoE), and paves the way for the future (e.g., towards the deployment of multi-sensory and ultra-realistic experiences). Although many advances around mediasync have been devised and deployed, this area of research is getting renewed attention to overcome remaining challenges in the next-generation (heterogeneous and ubiquitous) media ecosystem. Given the significant advances in this research area, its current relevance and the multiple disciplines it involves, the availability of a reference book on mediasync becomes necessary. This book fills the gap in this context. In particular, it addresses key aspects and reviews the most relevant contributions within the mediasync research space, from different perspectives. Mediasync: Handbook on Multimedia Synchronization is the perfect companion for scholars and practitioners that want to acquire strong knowledge about this research area, and also approach the challenges behind ensuring the best mediated experiences, by providing the adequate synchronization between the media elements that constitute these experiences

I-centric User Interaction

Die Vision I-centric Communications bedeutet, einen uneingeschränkten Blick auf das menschliche Kommunikationsverhalten zu werfen, um Kommunikationssysteme entsprechend daran angepasst zu entwickeln. Diese Vision definiert einen benutzerorientierten Ansatz zur Erstellung von Diensten und Anwendungen. Dies setzt zunächst eine Analyse der Benutzeranforderungen voraus, um geeignete Systeme und Dienste zu entwerfen. Anstatt Technologie-fokussierte Lösungen ohne jegliche Anpassung an die jeweiligen Personen anzubieten, sollte ein I-centric System seine Dienste ohne sichtbare technische Details und unter Berücksichtigung von Benutzerpräferenzen sowie der Benutzerumgebung darbieten. Der Vision von I-centric Communications folgend, stellt die vorliegende Arbeit einen Ansatz zur Realisierung der Idee von I-centric User Interaction vor. Dieser Ansatz erweitert und vervollständigt die Vision durch verbesserte Benutzerinteraktionsfähigkeiten. Diese Dissertation zeigt, dass es möglich ist, Kommunikationssysteme zu realisieren, die die Interaktion zwischen Benutzern und Diensten ohne Einschränkung auf bestimmte Technologien für Benutzerschnittstellen sowie in personalisierter und umgebungsberücksichtigende Art und Weise unterstützen. Derartig verbesserte Benutzerinteraktion wird die Akzeptanz und die Benutzung von Diensten erhöhen. Einerseits soll die Benutzerinteraktion verschiedene Arten von Technologien für Benutzerschnittstellen unterstützen, durch die die Geräte-Unabhängigkeit und der ständige Zugang zu den Diensten ermöglicht werden. Entsprechend dem aktuellem Kontext und der Absicht können die Benutzer die bevorzugte und geeignete Art der Interaktion wählen. Andererseits soll die Interaktion selbst den Benutzerpräferenzen sowie der jeweiligen Umgebung angepasst werden. Dementsprechend diskutiert die vorliegende Arbeit diese unterschiedlichen Problembereiche, identifiziert die notwendigen Funktionen und bietet entsprechende Lösungsansätze jeweils. Die Arbeit präsentiert und analysiert zunächst die Vision I-centric Communications mit Hinblick auf den Aspekt der Benutzerinteraktion. Basierend auf den identifizierten Anforderungen wurde ein Ansatz zur Realisierung von I-centric User Interaction entwickelt. Dieser Ansatz, der in dieser Arbeit vorgestellt wird, spezifiziert ein Service Adaptation Framework und einzelne Modelle für Generische Benutzerinteraktion , für Personalisierung sowie für Ambient Awareness , die sich jeweils auf die identifizierten Problembereiche konzentrieren. Abschließend präsentiert die vorliegende Arbeit Ergebnisse einer prototypischen Realisierung des dargelegten Ansatzes. Die Ergebnisse demonstrieren die Einsetzbarkeit der entwickelten Konzepte und die Erfüllung der Vision von I-centric User Interaction . Die Forschungsarbeit im Bereich I-centric Communications wurde in Kooperation zwischen dem Lehrstuhl für Offene Kommunikationssysteme (OKS) der Technischen Universität Berlin (TUB) und dem Fraunhofer Institut FOKUS durchgeführt. Die Vision sowie das Referenzmodell für I-centric Communications , die in der vorliegenden Arbeit vorgestellt werden, sind Ergebnisse dieser Kooperation. Die Forschungsschwerpunkte der Kooperation zwischen TUB und FOKUS waren das Generelle Modell für I-centric Dienste , die Dienstplattform für I-centric Dienste sowie ein Ansatz zur Interaktion zwischen Nutzern und I-centric Dienste . Die vorliegende Arbeit konzentriert sich auf den Ansatz I-centric User Interaction , der die Interaktion zwischen Nutzern und den Diensten betrachtet. Die Aspekte der I-centric Dienste werden in der vorliegenden Arbeit nicht betrachtet. Diese Aspekte wurden in einer zweiten Dissertation von Stefan Arbanowski, Fraunhofer FOKUS, analysiert und ausgearbeitet. Die Ergebnisse dieser Arbeit wurden in verschiedenen nationalen und internationalen Forschungsprojekten (BMBF LiveFutura, BMBF PI-AVIda, BMBF VHE-UD, IST WSI, IST WWRI), Standardisierungsgremien (OMG, WWRF), Konferenzpapieren sowie Zeitschriften eingebracht, um die Vision von I-centric Communications einem größeren Auditorium vorzustellen.The vision of I-centric Communications means to take an unlimited look at human communication behavior and to adapt the activities of communication systems to it. This vision defines a user-centered approach for the realization of services and applications. It requires to start analyzing user demands to design suitable systems and services. Instead of just providing technology-focused solutions without any adaptation to individuals, an I-centric system should provide services hiding technical details and considering the individual s preferences as well as the individual s environment. Following the vision of I-centric Communications, this thesis introduces an approach to realize I-centric User Interaction. This approach enhances and completes the vision by providing advanced user interaction capabilities. It answers the question whether it is possible to realize a communication system, which allows the interaction between user and services without any restriction to specific user interface technologies and in a personalized as well as ambient aware manner. Such enhanced user interaction will lead to a higher acceptance and increased usage of services. On the one hand, the user interaction shall support different kinds of user interface technologies enabling Device Independence and ubiquitous access to the services. According to their current context and intended action, users can select the preferred and suitable way of interaction. On the other hand, the user interaction shall be adapted to the user s preferences and to the user s environment. Accordingly, this work discusses these different areas of concern, identifies necessary functions, and provides suitable solutions for each. First, the thesis introduces and analyses the vision of I-centric Communications with special regard to the aspect of user interaction. Based on the identified requirements and areas of concern, an approach to realize I-centric User Interaction was developed. The approach, presented in this thesis, specifies a Service Adaptation Framework and individual models for Personalization, for Ambient Awareness, and for Generic User Interaction focusing on the respective areas of concern. Finally, the thesis illustrates the results from the prototypical implementation of the presented approach, which has been pursued in several projects in parallel. These results demonstrate the applicability of the developed concepts and the fulfillment of the vision of I-centric User Interaction. The work in the area of I-centric Communications was carried out in cooperation of the Department for Open Communication Systems (OKS) at the Technical University Berlin (TUB) and the Fraunhofer Institute FOKUS. The vision and the reference model for I-centric Communications, introduced in this thesis, are results of this cooperation. The main research directions for the cooperation between TUB and FOKUS have been a general model for I-centric services, the service platform for I-centric services, and an approach for the interaction of users with I-centric services. This thesis focuses on an approach for I-centric User Interaction. The general aspects of I-centric services as defined by the vision are out of scope of this thesis. Nevertheless, these aspects have been analyzed by Stefan Arbanowski, researcher at Fraunhofer FOKUS, in a second PhD thesis in parallel. The results of this work have been contributed to different national and international projects (BMBF LiveFutura, BMBF PI-AVIda, BMBF VHE-UD, IST WSI, IST WWRI), standardization bodies (OMG, WWRF), conferences papers, and journals by introducing the vision of I-centric Communications to a larger auditorium, and by exploiting parts of the developed I-centric systems

New Frontiers in Universal Multimedia Access

Universal Multimedia Access (UMA) refers to the ability to access by any user to the desired multimedia content(s) over any type of network with any device from anywhere and anytime. UMA is a key framework for multimedia content delivery service using metadata. This report consists of three parts. The first part of this report analyzes the state-of-the-art technologies in UMA, identifies the key issues and gives what are the new challenges that still remain to be resolved in UMA. The key issues in UMA include the adaptation of multimedia contents to bridge the gap between content creation and consuming, standardized metadata description that facilitates the adaptation (e.g. MPEG-7, MPEG-21 DIA, CC/PP), and UMA system designing considering its target application. The second part introduces our approach towards these challenges; how to jointly adapt multimedia contents including different modalities and balance their presentation in an optimal way. A scheme for adapting audiovisual contents and its metadata (text) to any screen is proposed to provide the best experience in browsing the desired content. The adaptation process is modeled as an optimization problem of the total value of the content provided to the user. The total content value is optimized by jointly controlling the balance between video and metadata presentation, the transformation of the video content, and the amount of the metadata to be presented. Experimental results show that the proposed adaptation scheme enables users to browse audiovisual contents with their metadata optimized to the screen size of their devices. The last part reports some potential UMA applications especially focusing on a universal access application to TV news archives as an example

Quality of experience aware adaptive hypermedia system

The research reported in this thesis proposes, designs and tests a novel Quality of Experience Layer (QoE-layer) for the classic Adaptive Hypermedia Systems (AHS) architecture. Its goal is to improve the end-user perceived Quality of Service in different operational environments suitable for residential users. While the AHS’ main role of delivering personalised content is not altered, its functionality and performance is improved and thus the user satisfaction with the service provided. The QoE Layer takes into account multiple factors that affect Quality of Experience (QoE), such as Web components and network connection. It uses a novel Perceived Performance Model that takes into consideration a variety of performance metrics, in order to learn about the Web user operational environment characteristics, about changes in network connection and the consequences of these changes on the user’s quality of experience. This model also considers the user’s subjective opinion about his/her QoE, increasing its effectiveness and suggests strategies for tailoring Web content in order to improve QoE. The user related information is modelled using a stereotype-based technique that makes use of probability and distribution theory. The QoE-Layer has been assessed through both simulations and qualitative evaluation in the educational area (mainly distance learning), when users interact with the system in a low bit rate operational environment. The simulations have assessed “learning” and “adaptability” behaviour of the proposed layer in different and variable home connections when a learning task is performed. The correctness of Perceived Performance Model (PPM) suggestions, access time of the learning process and quantity of transmitted data were analysed. The results show that the QoE layer significantly improves the performance in terms of the access time of the learning process with a reduction in the quantity of data sent by using image compression and/or elimination. A visual quality assessment confirmed that this image quality reduction does not significantly affect the viewers’ perceived quality that was close to “good” perceptual level. For qualitative evaluation the QoE layer has been deployed on the open-source AHA! system. The goal of this evaluation was to compare the learning outcome, system usability and user satisfaction when AHA! and QoE-ware AHA systems were used. The assessment was performed in terms of learner achievement, learning performance and usability assessment. The results indicate that QoE-aware AHA system did not affect the learning outcome (the students have similar-learning achievements) but the learning performance was improved in terms of study time. Most significantly, QoE-aware AHA provides an important improvement in system usability as indicated by users’ opinion about their satisfaction related to QoE

The web as a runtime in mobile context

Web-teknologiat kehitettiin alun perin kuvaamaan staattisten web-sivujen sisältöä. Web-selainten suosion vuoksi samoja teknologioita hyödynnetään nykyisin myös sovellusten toteuttamiseen käyttäen web-selainta niiden suorittamiseen vuorovaikutteisesti. Web-teknologioiden suosiosta huolimatta ne sisältävät useita ongelmia ohjelmistojen toteuttamisen näkökulmasta. Lisäksi mobiililaitteiden rajoitukset tekevät kaikilla laitteilla toimivien sovellusten toteuttamisesta haasteellista. Tämän vuoksi uusia ohjelmistoalustoja on kehitetty ratkaisemaan web-selainten asettamia rajoituksia. Tässä diplomityössä koostetaan vaatimukset mobiililaitteissa toimiville web-sovelluksille. Tämän lisäksi web-sovelluksille luodaan luokitusjärjestelmä ja tärkeimmät web-sovelluskehitykseen liittyvät web-teknologiat ja ohjelmistoalustat esitellään. Esimerkkisovellus toteutetaan käyttäen web-teknologioita ja hyödyntäen ohjelmistoalustan ominaisuuksia. Lisäksi esimerkkisovellus arvioidaan määritettyä vaatimusmäärittelyä vastaan. Arviointi paljasti lukuisia haasteita, jotka liittyivät web-teknologioiden puutteelliseen ilmaisuvoimaan, yhteentoimivuuteen ja ohjelmistoalustan toiminnallisuuteen. Tästä huolimatta esimerkkisovellus toteutti sille asetetut vaatimukset työpöytäohjelmistotasoisesta toiminnallisuudesta.Web technologies were initially designed to facilitate the creation of static web pages. However, the ubiquity of the web browser has motivated the use of the same technologies as a basis for desktop-style applications which are executed within the web browser and have their characteristics such as high interactivity. Despite the popularity of web applications, there exists various problems due to the fact that established web technologies were not specified with applications in mind. In addition, the constraints introduced by mobile devices challenge the ubiquity of such applications. On this account, new platforms have emerged extending the capabilities of web browsers. In this thesis, the requirements for client-side web applications in mobile context are synthesized. Moreover, a taxonomy for web applications is drawn and client-side web technologies and major software platforms relevant to the client-side web applications are discussed. Furthermore, an application concept implementation developed using web technologies leveraging the capabilities of the major mobile platform is presented and evaluated against the defined requirements. The evaluation revealed various problems related to limited expressiveness of web technologies, interoperability and platform functionality. Regardless, the implementation provided a level of functionality comparable to that of native applications

Contributions to presence-based systems for deploying ubiquitous communication services

Next-Generation Networks (NGNs) will converge the existing fixed and wireless networks. These networks rely on the IMS (IP Multimedia Subsystem), introduced by the 3GPP. The presence service came into being in instant messaging applications. A user¿s presence information consists in any context that is necessary for applications to handle and adapt the user's communications. The presence service is crucial in the IMS to deploy ubiquitous services. SIMPLE is the standard protocol for handling presence and instant messages. This protocol disseminates users' presence information through subscriptions, notifications and publications. SIMPLE generates much signaling traffic for constantly disseminating presence information and maintaining subscriptions, which may overload network servers. This issue is even more harmful to the IMS due to its centralized servers. A key factor in the success of NGNs is to provide users with always-on services that are seamlessly part of their daily life. Personalizing these services according to the users' needs is necessary for the success of these services. To this end, presence information is considered as a crucial tool for user-based personalization. This thesis can be briefly summarized through the following contributions: We propose filtering and controlling the rate of presence publications so as to reduce the information sent over access links. We probabilistically model presence information through Markov chains, and analyzed the efficiency of controlling the rate of publications that are modeled by a particular Markov chain. The reported results show that this technique certainly reduces presence overload. We mathematically study the amount of presence traffic exchanged between domains, and analyze the efficiency of several strategies for reducing this traffic. We propose an strategy, which we call Common Subscribe (CS), for reducing the presence traffic exchanged between federated domains. We compare this strategy traffic with that generated by other optimizations. The reported results show that CS is the most efficient at reducing presence traffic. We analyze the load in the number of messages that several inter-domain traffic optimizations cause to the IMS centralized servers. Our proposed strategy, CS, combined with an RLS (i.e., a SIMPLE optimization) is the only optimization that reduces the IMS load; the others increase this load. We estimate the efficiency of the RLS, thereby concluding that the RLS is not efficient under certain circumstances, and hence this optimization is discouraged. We propose a queuing system for optimizing presence traffic on both the network core and access link, which is capable to adapt the publication and notification rate based on some quality conditions (e.g, maximum delay). We probabilistically model this system, and validate it in different scenarios. We propose, and implement a prototype of, a fully-distributed platform for handling user presence information. This approach allows integrating Internet Services, such as HTTP or VoIP, and optimizing these services in an easy, user-personalized way. We have developed SECE (Sense Everything, Control Everything), a platform for users to create rules that handle their communications and Internet Services proactively. SECE interacts with multiple third-party services for obtaining as much user context as possible. We have developed a natural-English-like formal language for SECE rules. We have enhanced SECE for discovering web services automatically through the Web Ontology Language (OWL). SECE allows composing web services automatically based on real-world events, which is a significant contribution to the Semantic Web. The research presented in this thesis has been published through 3 book chapters, 4 international journals (3 of them are indexed in JCR), 10 international conference papers, 1 demonstration at an international conference, and 1 national conferenceNext-Generation Networks (NGNs) son las redes de próxima generación que soportaran la convergencia de redes de telecomunicación inalámbricas y fijas. La base de NGNs es el IMS (IP Multimedia Subsystem), introducido por el 3GPP. El servicio de presencia nació de aplicaciones de mesajería instantánea. La información de presencia de un usuario consiste en cualquier tipo de información que es de utilidad para manejar las comunicaciones con el usuario. El servicio de presencia es una parte esencial del IMS para el despliegue de servicios ubicuos. SIMPLE es el protocolo estándar para manejar presencia y mensajes instantáneos en el IMS. Este protocolo distribuye la información de presencia de los usuarios a través de suscripciones, notificaciones y publicaciones. SIMPLE genera mucho tráfico por la diseminación constante de información de presencia y el mantenimiento de las suscripciones, lo cual puede saturar los servidores de red. Este problema es todavía más perjudicial en el IMS, debido al carácter centralizado de sus servidores. Un factor clave en el éxito de NGNs es proporcionar a los usuarios servicios ubicuos que esten integrados en su vida diaria y asi interactúen con los usuarios constantemente. La personalización de estos servicios basado en los usuarios es imprescindible para el éxito de los mismos. Para este fin, la información de presencia es considerada como una herramienta base. La tesis realizada se puede resumir brevemente en los siguientes contribuciones: Proponemos filtrar y controlar el ratio de las publicaciones de presencia para reducir la cantidad de información enviada en la red de acceso. Modelamos la información de presencia probabilísticamente mediante cadenas de Markov, y analizamos la eficiencia de controlar el ratio de publicaciones con una cadena de Markov. Los resultados muestran que este mecanismo puede efectivamente reducir el tráfico de presencia. Estudiamos matemáticamente la cantidad de tráfico de presencia generada entre dominios y analizamos el rendimiento de tres estrategias para reducir este tráfico. Proponemos una estrategia, la cual llamamos Common Subscribe (CS), para reducir el tráfico de presencia entre dominios federados. Comparamos el tráfico generado por CS frente a otras estrategias de optimización. Los resultados de este análisis muestran que CS es la estrategia más efectiva. Analizamos la carga en numero de mensajes introducida por diferentes optimizaciones de tráfico de presencia en los servidores centralizados del IMS. Nuestra propuesta, CS, combinada con un RLS (i.e, una optimización de SIMPLE), es la unica optimización que reduce la carga en el IMS. Estimamos la eficiencia del RLS, deduciendo que un RLS no es eficiente en ciertas circunstancias, en las que es preferible no usar esta optimización. Proponemos un sistema de colas para optimizar el tráfico de presencia tanto en el núcleo de red como en la red de acceso, y que puede adaptar el ratio de publicación y notificación en base a varios parametros de calidad (e.g., maximo retraso). Modelamos y analizamos este sistema de colas probabilísticamente en diferentes escenarios. Proponemos una arquitectura totalmente distribuida para manejar las información de presencia del usuario, de la cual hemos implementado un prototipo. Esta propuesta permite la integracion sencilla y personalizada al usuario de servicios de Internet, como HTTP o VoIP, asi como la optimizacón de estos servicios. Hemos desarrollado SECE (Sense Everything, Control Everything), una plataforma donde los usuarios pueden crear reglas para manejar todas sus comunicaciones y servicios de Internet de forma proactiva. SECE interactúa con una multitud de servicios para conseguir todo el contexto possible del usuario. Hemos desarollado un lenguaje formal que parace como Ingles natural para que los usuarios puedan crear sus reglas. Hemos mejorado SECE para descubrir servicios web automaticamente a través del lenguaje OWL (Web Ontology Language)

Supervision de contenus multimédia : adaptation de contenu, politiques optimales de préchargement et coordination causale de flux

La qualité des systèmes d'informations distribués dépend de la pertinence du contenu mis à disposition, de la réactivité du service ainsi que de la cohérence des informations présentées. Nos travaux visent à améliorer ces trois critères de performance et passent par la prise en compte des caractéristiques de l'utilisateur, des ressources disponibles ou plus généralement du contexte d'exécution. Par conséquent, cette thèse comporte trois volets. Le premier volet se place dans le cadre de l'adaptation de systèmes d’information déployés dans des contextes dynamiques et stochastiques. Nous présentons une approche où des agents d’adaptation appliquent des politiques de décision séquentielle dans l'incertain. Nous modélisons ces agents par des Processus Décisionnels de Markov (PDM) selon que le contexte soit observable ou seulement partiellement observable (PDM Partiellement Observables). Dans le cas d’un service mobile de consultation de films, nous montrons en particulier qu’une politique d'adaptation de ce service à des ressources limitées peut être nuancée selon l'intérêt de l'utilisateur, estimé grâce à l’évaluation des signaux de retour implicite. Dans le deuxième volet, nous nous intéressons à l'optimisation de la réactivité d'un système qui propose des contenus hypermédia. Nous nous appuyons sur des techniques de préchargement pour réduire les latences. Comme précédemment, un PDM modélise les habitudes des utilisateurs et les ressources disponibles. La force de ce modèle réside dans sa capacité à fournir des politiques optimales de préchargement. Les premières politiques que nous obtenons sont simples. Nous enrichissons alors le modèle pour dériver des politiques de préchargement plus complexes et plus agressives et montrons leurs performances par simulation. Afin de personnaliser nos stratégies optimales nous proposons finalement un modèle PDMPO dont les politiques s'adaptent aux profils des utilisateurs. Le troisième volet se place dans le contexte des applications multimédia interactives distribuées et concerne le contrôle de la cohérence des flux multimédia répartis. Dans un tel contexte, plusieurs mécanismes de synchronisation sont nécessaires et plusieurs ordres logiques (fifo, causal, total) s'avèrent utiles. Nous proposons une boîte à outils capable de gérer plusieurs protocoles d’ordre partiel et d'assurer une délivrance correcte de chaque message, en respectant tous les ordres qui lui ont été imposés. Nous décrivons ensuite l’intégration des tolérances humaines vis-à-vis des courtes incohérences causales dans notre boîte à outils. Nos simulations montrent que de meilleures performances sont obtenues par cette méthode comparativement à d’autres approches, comme la causalité classique ou la Δ-causalité. ABSTRACT : Distributed systems information quality depends on service responsiveness, data consistency and its relevance according to user interests. The thesis aims to improve these three performance criteria by taking into account user characteristics, available ressources or more generally execution context. Naturally, the document is organized in three main parts. The first part discusses adaptation policies for information systems that are subject to dynamic and stochastic contexts. In our approach adaptation agents apply sequential decisional policies under uncertainty. We focus on the modeling of such decisional processes depending on whether the context is fully or partially observable. We use Markov Decision Processes (MDP) and Partially Observable MDP (POMDP) for modeling a movie browsing service in a mobile environment. Our model derives adaptation policies for this service that take into account the limited (and observable) resources. These policies are further refined according to the (partially observable) users’ interest level estimated from implicit feedback. Our theoretical models are validated through numerous simulations. The second part deals with hypermedia content delivery aiming to reduce navigation latencies by means of prefetching. As previously, we build upon an MDP model able to derive optimal prefetching policies integrating both user behaviour and ressource availability. First, we extend this model and propose more complex and aggressive policies. Second, the extended model is enriched by taking into account user's profile and therefore provides finer prefetching policies. It is worth noting that this model issues personnalized policies without explicily manipulating user profiles. The proposed extensions and the associated policies are validated through comparison with the original model and some heuristic approches. Finally, the third part considers multimedia applications in distributed contexts. In these contexts, highly interactive collaborative applications need to offer each user a consistent view of the interactions represented by the streams exchanged between dispersed groups of users. At the coordination level, strong ordering protocols for capturing and delivering streams' interactions (e.g. CAUSAL, TOTAL order) may be too expensive due to the variability of network conditions. We build upon previous work on expressing streams causality and propose a flexible coordination middleware for integrating different delivery modes (e.g. FIFO, CAUSAL, TOTAL) into a single channel (with respect to each of these protocols). Moreover, the proposed abstract channel can handle the mix of any partial or total order protocols. Integrating perceptual tolerance in our middleware, provides us with a coordination toolkit that performs better than Δ-causality, usually considered the best solutio