Visual Development Environment for Semantically Interoperable Smart Cities Applications

International audienceThis paper presents an IoT architecture for the semantic interoperability of diverse IoT systems and applications in smart cities. The architecture virtualizes diverse IoT systems and ensures their modelling and representation according to common standards-based IoT ontologies. Furthermore, based on this architecture, the paper introduces a first-of-a-kind visual development environment which eases the development of semantically interoperable applications in smart citites. The development environment comes with a range of visual tools, which enable the assembly of non-trivial data-driven applications in smart cities, including applications that leverage data streams from diverse IoT systems. Moreover, these tools allow developers to leverage the functionalities and building blocks of the presented architecture. Overall, the introduced visual environment advances the state of the art in IoT developments for smart cities towards the direction of semantic interoperability for data driven application

Intergiciel d'intergiciels adaptable à base de Services, Composants et Aspects

Cette habilitation à diriger des recherches présente mes travaux sur le génie logiciel des intergiciels, domaine à la croisée de l’informatique répartie et du génie logiciel. L’intergiciel est la couche logicielle permettant de s’abstraire de l’hétérogénéité des technologies de l’informatique distribuée et de répondre aux besoins d’interopérabilité, de portabilité, d’adaptation et de séparation des préoccupations des applications réparties. Mes travaux ont été guidés par deux questions de recherche ouvertes : 1) quel est le paradigme de programmation le plus approprié pour les applications réparties ? 2) quelle est l’organisation la plus appropriée pour l’intergiciel ?La première partie présente une synthèse de mes travaux et contributions. Premièrement, mes travaux ont porté sur la transition des objets vers les composants CORBA donnant lieu à deux contributions majeures : le langage de script CorbaScript standardisé auprès de l’OMG et la plate-forme OpenCCM pour le développement, le déploiement, l’exécution et l’administration d’applications réparties à base de composants CORBA. Deuxièmement, je me suis intéressé à la conception de canevas intergiciels hautement adaptables. Ces travaux basés sur les composants réflexifs Fractal ont donné lieu à un cadre de programmation par attributs sur lequel trois canevas flexibles pour la gestion du transactionnel, le déploiement de systèmes distribués hétérogènes et les composants Java temps-réels ont été bâtis. Enfin, mes travaux ont porté sur la proposition du modèle Services Composants Aspects (SCA) et l’intergiciel d’intergiciels FraSCAti.La deuxième partie opère un zoom sur le projet FraSCAti. La contribution scientifique de ce projet est de proposer un intergiciel réflexif pour l’informatique orientée service combinant deux idées originales : la notion d’intergiciel d’intergiciels et le modèle Services Composants Aspects réflexif. Partant du constat qu’il n’existe pas d’intergiciel universel capable de couvrir l’ensemble des besoins de toutes les applications distribuées, le projet FraSCAti propose un canevas intergiciel extensible pour l’intégration et la composition élégante des intergiciels et technologies SOA existants, c’est-à-dire un intergiciel d’intergiciels. Le modèle SCA réflexif est quant à lui le mariage fécond du standard OASIS Service Component Architecture (SCA), du modèle de composants Fractal et de la programmation orientée aspects (AOP). Dans ce modèle, tout est composant réflexif permettant ainsi d’adapter dynamiquement aussi bien les applications métiers, l’intergiciel, les liaisons de communication réseau que les aspects non fonctionnels. Cette contribution a été appliquée sur l’orchestration de services à large échelle, la construction de systèmes de systèmes et une plate-forme distribuée multi-nuages. La dernière partie dresse un bilan des contributions et présente mes perspectives de recherche centrées sur le génie logiciel pour l’informatique en nuage (cloud computing)

Self-Healing Protocols for Connectivity Maintenance in Unstructured Overlays

In this paper, we discuss on the use of self-organizing protocols to improve the reliability of dynamic Peer-to-Peer (P2P) overlay networks. Two similar approaches are studied, which are based on local knowledge of the nodes' 2nd neighborhood. The first scheme is a simple protocol requiring interactions among nodes and their direct neighbors. The second scheme adds a check on the Edge Clustering Coefficient (ECC), a local measure that allows determining edges connecting different clusters in the network. The performed simulation assessment evaluates these protocols over uniform networks, clustered networks and scale-free networks. Different failure modes are considered. Results demonstrate the effectiveness of the proposal.Comment: The paper has been accepted to the journal Peer-to-Peer Networking and Applications. The final publication is available at Springer via http://dx.doi.org/10.1007/s12083-015-0384-

Self-management for large-scale distributed systems

Autonomic computing aims at making computing systems self-managing by using autonomic managers in order to reduce obstacles caused by management complexity. This thesis presents results of research on self-management for large-scale distributed systems. This research was motivated by the increasing complexity of computing systems and their management. In the first part, we present our platform, called Niche, for programming self-managing component-based distributed applications. In our work on Niche, we have faced and addressed the following four challenges in achieving self-management in a dynamic environment characterized by volatile resources and high churn: resource discovery, robust and efficient sensing and actuation, management bottleneck, and scale. We present results of our research on addressing the above challenges. Niche implements the autonomic computing architecture, proposed by IBM, in a fully decentralized way. Niche supports a network-transparent view of the system architecture simplifying the design of distributed self-management. Niche provides a concise and expressive API for self-management. The implementation of the platform relies on the scalability and robustness of structured overlay networks. We proceed by presenting a methodology for designing the management part of a distributed self-managing application. We define design steps that include partitioning of management functions and orchestration of multiple autonomic managers. In the second part, we discuss robustness of management and data consistency, which are necessary in a distributed system. Dealing with the effect of churn on management increases the complexity of the management logic and thus makes its development time consuming and error prone. We propose the abstraction of Robust Management Elements, which are able to heal themselves under continuous churn. Our approach is based on replicating a management element using finite state machine replication with a reconfigurable replica set. Our algorithm automates the reconfiguration (migration) of the replica set in order to tolerate continuous churn. For data consistency, we propose a majority-based distributed key-value store supporting multiple consistency levels that is based on a peer-to-peer network. The store enables the tradeoff between high availability and data consistency. Using majority allows avoiding potential drawbacks of a master-based consistency control, namely, a single-point of failure and a potential performance bottleneck. In the third part, we investigate self-management for Cloud-based storage systems with the focus on elasticity control using elements of control theory and machine learning. We have conducted research on a number of different designs of an elasticity controller, including a State-Space feedback controller and a controller that combines feedback and feedforward control. We describe our experience in designing an elasticity controller for a Cloud-based key-value store using state-space model that enables to trade-off performance for cost. We describe the steps in designing an elasticity controller. We continue by presenting the design and evaluation of ElastMan, an elasticity controller for Cloud-based elastic key-value stores that combines feedforward and feedback control