Composition and Formal Validation in Reactive Adaptive Middleware

Nowadays, adaptive middleware plays an important role in the design of applications in ubiquitous and ambient computing. Currently most of these systems manage the adaptation at the middleware intermediary layer. Dynamic adaptive middleware are then decomposed into two levels : a first one to simplify the development of distributed systems using devices, a second one to perform dynamic adaptations within the first level. In this report we consider component-based middleware and a corresponding compositional adaptation. Indeed, the composition often involves conflicts between concurrent adaptations. Thus we study how to maintain consistency of the application in spite of changes of critical components and conflicts that may appear when we compose some component assemblies. Relying on formal methods, we provide a well defined representation of component behaviors. In such a setting, model checking techniques are applied to ensure that concurrent access does not violate expected and acceptable behaviors of critical components.De nos jours, les middlewares adaptatifs et réactifs jouent un role important dans la conception d'applications dans le domaine de l'Informatique ubiquitaire et ambiante. Généralement, ces systèmes réalisent cette adaptation au niveau intermédiaire du middleware. Ainsi, les middlewares adaptatifs sont décomposés en deux parties: une première partie qui permet un développement simplifié des systèmes distribués utilisant des dispositifs, une seconde qui réalise les adaptations dynamiques de la première partie. Dans ce rapport nous considérons des middlewares à base de composants et une adapaptation compositionnelle. Mais souvent lors d'une composition certaines adaptations concurrentes s'avèrent conflictuelles. Pour résoudre ce problème, nous étudions comment préserver la consistence d'une application lors de changements concernant certains composants critiques, avec des conflits qui peuvent apparaitre quand on compose des assemblages de composants. Nous utilisons des méthodes formelles pour modéliser le comportement des composants afin de bénéficier des techniques de vérification par model checking et ainsi prouver que des accès concurrents respectent les comportements acceptables des composants critiques

Quality of service support for service discovery and selection in service oriented computing environment

Service oriented computing (SOC) represents a new generation of web architecture. Central to SOC is the notion of services, which are self-contained, self-describing, modular applications that can be published, located, and invoked across the Internet. The services represent capability, which can be anything from simple operations to complicated business processes. This new architecture offers great potential for e-commerce applications, where software agents can automatically find and select the services that best serve a consumer's interests. Many techniques have been proposed for discovery and selection of services, most of which have been constructed without a formal Quality of Service (QoS) model or much regard to understanding the needs of consumers. This thesis aims to provide QoS support for the entire SOC life cycle, namely: (i) extend current approaches to service discovery that allow service providers to advertise their services in a format that supports quality specifications, and allows service consumers to request services by stating required quality levels, (ii) support matchmaking between advertised and requested services based on functional as well as quality requirements, (iii) perform QoS assessment to support consumers in service selection. Many techniques exists for performing QoS assessment, most of which are based on collecting quality ratings from the users of a service. This thesis argues that collecting quality ratings alone from the users is not sufficient for deriving a reliable and accurate quality measure for a service. This is because different users often have different expectations and judgements on the quality of a service and their ratings tend to be closely related to these expectations, i.e., how their expectations are met. The thesis proposes a new model for QoS assessment, based on user expectations that collects expectations as well as ratings from the users of a service, then calculates the QoS using only the ratings which were judged on similar expectations.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Quality of service support for service discovery and selection in service oriented computing environment

Service oriented computing (SOC) represents a new generation of web architecture. Central to SOC is the notion of services, which are self-contained, self-describing, modular applications that can be published, located, and invoked across the Internet. The services represent capability, which can be anything from simple operations to complicated business processes. This new architecture offers great potential for e-commerce applications, where software agents can automatically find and select the services that best serve a consumer's interests. Many techniques have been proposed for discovery and selection of services, most of which have been constructed without a formal Quality of Service (QoS) model or much regard to understanding the needs of consumers. This thesis aims to provide QoS support for the entire SOC life cycle, namely: (i) extend current approaches to service discovery that allow service providers to advertise their services in a format that supports quality specifications, and allows service consumers to request services by stating required quality levels, (ii) support matchmaking between advertised and requested services based on functional as well as quality requirements, (iii) perform QoS assessment to support consumers in service selection. Many techniques exists for performing QoS assessment, most of which are based on collecting quality ratings from the users of a service. This thesis argues that collecting quality ratings alone from the users is not sufficient for deriving a reliable and accurate quality measure for a service. This is because different users often have different expectations and judgements on the quality of a service and their ratings tend to be closely related to these expectations, i.e., how their expectations are met. The thesis proposes a new model for QoS assessment, based on user expectations that collects expectations as well as ratings from the users of a service, then calculates the QoS using only the ratings which were judged on similar expectations