Sistemas computacionais são constituídos por componentes de hardware e software que podem eventualmente falhar. Por esse motivo, o mecanismo de transação sempre foi imprescindível para a construção de sistemas robustos. O suporte transacional para a tecnologia Web services foi definido em agosto de 2005, num conjunto de três especificações denominadas WS-Coordination, WS-AtomicTransaction e WS-BusinessActivity. Juntas, essas especificações definem um alicerce sobre o qual aplicações robustas baseadas em Web services podem ser construídas. Nesta dissertação realizamos um estudo sobre transações atômicas em ambientes Web services. Em particular, estendemos o gerenciador de transações presente no servidor de aplicações JBoss, de modo que ele passasse a comportar transações distribuídas envolvendo Web services. Além disso, avaliamos o desempenho desse gerenciador de transações quando ele emprega cada um dos seguintes mecanismos de chamada remota: Web services/SOAP, CORBA/IIOP e JBoss Remoting. Finalmente, realizamos experimentos de escalabilidade e interoperabilidade. / Computing systems consist of a multitude of hardware and software components that may fail. For this reason, the transaction mechanism has always been essential for the development of robust systems. Transactional support for the Web services technology was defined in August 2005, in a set of three specifications, namely WS-Coordination, WS-AtomicTransaction, and WS-BusinessActivity. Together, such specifications enable the development of robust Web services applications. In this dissertation we studied atomic transactions in the Web services realm. Particularly, we added Web services atomic transaction support to the existing JBoss application server transaction manager. Furthermore, we evaluated the performance of this transaction manager when it employs each of the following remote method invocation mechanisms: Web services/SOAP, CORBA/IIOP and JBoss Remoting. Finally, we performed scalability and interoperability experiments.

Sistemas computacionais são constituídos por componentes de hardware e software que podem eventualmente falhar. Por esse motivo, o mecanismo de transação sempre foi imprescindível para a construção de sistemas robustos. O suporte transacional para a tecnologia Web services foi definido em agosto de 2005, num conjunto de três especificações denominadas WS-Coordination, WS-AtomicTransaction e WS-BusinessActivity. Juntas, essas especificações definem um alicerce sobre o qual aplicações robustas baseadas em Web services podem ser construídas. Nesta dissertação realizamos um estudo sobre transações atômicas em ambientes Web services. Em particular, estendemos o gerenciador de transações presente no servidor de aplicações JBoss, de modo que ele passasse a comportar transações distribuídas envolvendo Web services. Além disso, avaliamos o desempenho desse gerenciador de transações quando ele emprega cada um dos seguintes mecanismos de chamada remota: Web services/SOAP, CORBA/IIOP e JBoss Remoting. Finalmente, realizamos experimentos de escalabilidade e interoperabilidade. / Computing systems consist of a multitude of hardware and software components that may fail. For this reason, the transaction mechanism has always been essential for the development of robust systems. Transactional support for the Web services technology was defined in August 2005, in a set of three specifications, namely WS-Coordination, WS-AtomicTransaction, and WS-BusinessActivity. Together, such specifications enable the development of robust Web services applications. In this dissertation we studied atomic transactions in the Web services realm. Particularly, we added Web services atomic transaction support to the existing JBoss application server transaction manager. Furthermore, we evaluated the performance of this transaction manager when it employs each of the following remote method invocation mechanisms: Web services/SOAP, CORBA/IIOP and JBoss Remoting. Finally, we performed scalability and interoperability experiments.

ITC/USA 2008 Conference Proceedings / The Forty-Fourth Annual International Telemetering Conference and Technical Exhibition / October 27-30, 2008 / Town and Country Resort & Convention Center, San Diego, California / The integrated Network Enhanced Telemetry (iNET) and Test and Training Enabling Architecture (TENA) projects are working to understand how TENA will perform in a Telemetry Network System. This paper discusses a demonstration prototype that is being used to investigate the use of TENA across a constrained test environment simulating iNET capabilities. Some of the key elements being evaluated are throughput, latency, memory utilization, memory footprint, and bandwidth. The results of these evaluations will be presented. Additionally, the paper briefly discusses modeling and metadata requirements for TENA and iNET.

Des logiciels complexes, assemblés à partir de nombreux composants préexistants, sont aujourd'hui utilisés pour des emplois de plus en plus critiques (télécommunication, ferroviaire, automobile...). Les risques encourus, aussi bien humains qu'économiques, exigent de pouvoir mettre en place dans ces systèmes des mécanismes de tolérance aux fautes flexibles et adaptables indépendamment des composants utilisés. Mais la complexification des logiciels pose problème, car les approches développées jadis pour assurer la sûreté de fonctionnement de petits systèmes ne leur sont plus applicables. Connues depuis longtemps, les architectures réflexives, en autorisant le découplage des aspects fonctionnels et non-fonctionnels d'un système, visent à résoudre ce problème. Jusqu'ici cependant, les approches proposées s'étaient limitées à des prototypes simples, souvent réalisés ex-nihilo pour expérimentation. Or la tolérance aux fautes est une propriété globale des systèmes considérés, qui requiert la prise en compte de tous les niveaux d'abstraction rencontrés. Dans cette thèse, nous étudions comment le paradigme réflexif peut être adapté pour permettre d'intégrer les considérations algorithmiques de la tolérance aux fautes (validité, observation, contrôle) aux contraintes architecturales rencontrées dans les systèmes complexes (abstraction, transparence, inter-opérabilité). Pour aborder cette problématique, nous développons un nouveau cadre conceptuel, la réflexivité multi-niveaux, et les concepts d'empreinte réflexive et de lien inter-niveaux qui lui sont associés. Nous validons ensuite la pertinence pratique de notre proposition en abordant la réplication de serveurs CORBA à brins d'exécution multiples (multithreaded) sur un exemple concret constitué de GNU/Linux et de l'ORB commercial ORBacus. Nous concluons finalement à la nécessité d'un nouveau paradigme de développement basé sur des composants rendus réflexifs dès leur réalisation.

Dissertação apresentada para obtenção do grau de Mestre em Redes e Serviços de Comunicação, na Faculdade de Engenharia da Universidade do Porto, sob a orientação do Professor Doutor José Ruela Simões Fernandes

<p>A Transaction Reproduction System (ARTSY) is a distributed system that enables secure transactions and reproductions of digital content over an insecure network. A field of application is reproductions of visual arts: A print workshop could for example use ARTSY to print a digital image that is located at a remote museum. The purpose of this master thesis project was to propose a specification for ARTSY and to show that it is technically feasible to implement it. </p><p>An analysis of the security threats in the ARTSY context was performed and a security model was developed. The security model was approved by a leading computer security expert. The security mechanisms that were chosen for the model were: Asymmetric cryptology, digital signatures, symmetric cryptology and a public key registry. A Software Requirements Specification was developed. It contains extra directives for image reproduction systems but it is possible to use it for an arbitrary type of reproduction system. A prototype of ARTSY was implemented using the Java programming language. The prototype uses XML to manage information and Java RMI to enable remote communication between its components. It was built as a platform independent system and it has been tested and proven to be operational on the Sun Solaris platform as well as the Win32 platform.</p>

A Transaction Reproduction System (ARTSY) is a distributed system that enables secure transactions and reproductions of digital content over an insecure network. A field of application is reproductions of visual arts: A print workshop could for example use ARTSY to print a digital image that is located at a remote museum. The purpose of this master thesis project was to propose a specification for ARTSY and to show that it is technically feasible to implement it. An analysis of the security threats in the ARTSY context was performed and a security model was developed. The security model was approved by a leading computer security expert. The security mechanisms that were chosen for the model were: Asymmetric cryptology, digital signatures, symmetric cryptology and a public key registry. A Software Requirements Specification was developed. It contains extra directives for image reproduction systems but it is possible to use it for an arbitrary type of reproduction system. A prototype of ARTSY was implemented using the Java programming language. The prototype uses XML to manage information and Java RMI to enable remote communication between its components. It was built as a platform independent system and it has been tested and proven to be operational on the Sun Solaris platform as well as the Win32 platform.

Component-based applications require runtime support to be able to guarantee non-functional properties. This report proposes an architecture for a real-time-capable, component-based runtime environment, which allows to separate non-functional and functional concerns in component-based software development. The architecture is presented with particular focus on three key issues: the conceptual architecture, an approach including implementation issues for splitting the runtime environment into a real-time-capable and a real-time-incapable part, and details of contract negotiation. The latter includes selecting component implementations for instantiantion based on their non-functional properties.

Parallel, adaptive Level-of-Detail in VR simulations. Parameters for efficient reuse of already calculated reductions are investigated. Choosen reduction algorithms are evaluated. Parameters for communication within the distributed application are determined. An implementation is introduced. / Paralleles, adaptives Level-of-Detail komplexer Objekten in VR-Simulationen. Die Parameter für eine effiziente Wiederverwendung bereits berechneter Reduktionen werden untersucht. Ausgewählte Reduktionsalgorithmen werden evaluiert. Die Parameter für die Kommunikation in der verteilten Applikation werden ermittelt. Eine Implementation wird vorgestellt.

Nous proposons une méthodologie pour l'analyse de la sûreté de fonctionnement d'un middleware, ou intergiciel, et caractériser son comportement en présence de fautes. Notre méthode est basée sur une analyse structurelle des intergiciels de communication, sur l'élaboration d'un modèle de fautes, une classification des modes de défaillance, et le développement d'un ensemble de techniques d'injection de faute adaptées à l'intergiciel. Nous avons validé notre approche en menant des campagnes d'injection de faute ciblant plusieurs implantations de la norme CORBA, et obtenu des mesures quantitatives de la robustesse des différents candidats testés. Nos travaux permettent à des intégrateurs de systèmes répartis critiques d'obtenir des assurances sur la robustesse des composants intergiciels qu'ils placent au coeur de leurs systèmes, et aux développeurs d'intergiciel d'obtenir des informations sur des points faibles de leurs produits.