Suchergebnisse

In light of the recent advances in the field of web engineering, along with the decrease of cost of cloud computing, service-oriented architectures rapidly became the leading solution in providing valuable services to clients. Following this trend, the composition of third-party services has become a successful paradigm for the development of robust and rich distributed applications, as well as automating business processes. With the availability of hundreds of thousands of web services and APIs, such integrations become cumbersome and tedious when performed manually. Furthermore, different clients may require different integration requirements and policies, which further complexifies the task. Moreover, providing such a solution that is both robust and scalable is a non-trivial task. Therefore, it becomes crucial to investigate how to efficiently coordinate the interactions between existing web services. As such, this thesis aims at investigating the underlying challenges in web service composition in the context of modern web development practices. We present an architectural framework to support the specification of web service compositions using a language-based approach, and show how we support their execution in a scalable manner using MEDLEY, a lightweight, event-driven platform. ; Au vu des dernières avancées dans le domaine de l'ingénierie web, ainsi qu'avec la baisse de coût du cloud computing, les architectures orientées services sont rapidement devenues la solution prépondérante pour fournir des services à valeur ajoutée aux clients. Suite à cette tendance, la composition de services tiers est devenue un paradigme de référence pour le développement d'applications robustes et riches, ou encore pour l'automatisation de processus métiers. Avec la disponibilité de centaines de milliers de services et APIs web, la réalisation de telles intégrations devient lourde et fastidieuse quand effectuée manuellement. Par ailleurs, chaque client peut exiger des besoins et politiques d'intégration différentes, ce qui ...

The connectivity generated by the Internet is opening new opportunities in service delivery since administrations are forming online alliances in order to deliver integrated value-adding services. However, due to lack of a step-by-step method for identification and further processing of services, the development of such composite e-Government services is usually ad-hoc. In this paper, we demonstrate how a systematic service composition can be accomplished: with the help of the proposed Service Description Worksheet, the e-Govemment Services can now be classified, searched for and composed into larger groups. This goal-driven approach can be used to understand the needs of different organizations and to depict the various functional characteristics of the cooperative processes in a declarative manner, suitable for prototyping projects in the public sector. Applying this method in the context of the Greek e-Govemment Services Framework, various services have been analysed, populating the worksheet database and leading to corresponding process models. © Springer-Verlag Berlin Heidelberg 2007.

In recent years, it has been made possible to compose exiting services when a user's request cannot be satisfied by a single web service. Web service composition is faced with several challenges among which is the rapid growth in the number of available web services leading to increased number of web services offering the same functionalities. The difference between similar services is Quality of Service (QoS) consisting of various non-functional factors such as execution time, availability, security, etc. As a result, multiple choices are possible in making a composition plan. Among numerous plans, selecting a composition plan that fulfills customer's requirements has become an important and time-consuming problem. In this paper, the researchers propose a semi-heuristic genetic algorithm that is a combination of both a heuristic method and the genetic algorithm. This heuristic method changes chromosomes based on unsatisfied constraints. Research findings show that the proposed method can be applied to find a composition plan that satisfies user's requirements more efficiently than other methods.

AbstractDuring the past decade, Web services (WS) have gained attention, as they provided the means for interoperability between loosely coupled distributed systems over the Web. Regardless of the platforms and technologies deployed in their development, by using WS, the aforementioned systems can seamlessly exchange messages and, thus, engage into business transactions over the global network. Nevertheless, these opportunities resulted in a wide plethora of available WS, making it hard for end‐users and composition engines to select the optimal service between two or more services with seemingly identical operational features. As a result, the WS composition engines often make decisions on the basis of the QoS criteria. In modern literature, many researchers have tried to confront the issue of QoS‐based composition, by applying multi‐criteria decision analysis (MCDA) methods often showing mixed results. This is due to the different characteristics of each MCDA method. In this work, we tried to identify the key criteria that should be taken into account when deciding the optimal MCDA method to use in a given scenario, on the basis of its unique business context, and in addition, we provide an empirical study in order to compare the advantages and disadvantages of the mostly used MCDA methods in the field of WS selection and composition. Copyright © 2014 John Wiley & Sons, Ltd.

Future IoT systems will be deployed in open environments where the functionality of millions of IoT devices that are heterogeneous will be abstracted. In such a large scale system manual service composition is not feasible and often erroneous. A self-organizing service composition is a well known approach to deal with the problems in IoT systems. In a self-organizing service composition, the service composition is a runtime and autonomous process and human intervention is minimal. The atomic components will interact among themselves in a decentralized manner to form complex composites according to a set of self-organizing rules. The features of a self-organizing software composition are aptly suitable for the IoT domain. Smart healthcare has provided affordable healthcare for patients and enables them to self manage emergencies. This paper aims to establish the suitability of a self-organizing service composition for the smart healthcare ecosystem with special focus on real time monitoring applications.

The advent of Service Oriented Architectures tends to promote a new kind of software architecture where services, exposing features accessible through highly standardized protocols, are composed in aloosely coupled way. In such a context, where services are likely to be replaced or used by a large numberof clients, the notion of Quality of Service (QoS), which focuses on the quality of the relationship between a service and its customers, becomes a key challenge. QoS deals with multiple concerns suchas security, reliability, performance (response time or availability), or even the cost of the service. Although much work has been carried out in the field of service composition, in particular leading to the elaboration of the BPEL4WS standard, the challenge of QoS management in service compositions still lacks flexible and reusable solutions offering a suitable level of abstraction.This thesis aims to ease QoS management in service compositions through a better separation of concerns. For this purpose, we designed QoSL4BP, a domain-specific language which allows QoS policy specification on service compositions. Such policies handle QoS constraints and mechanisms, both at pre-deployment time and runtime, by use of a limited set of high level primitives. By encapsulating the expertise of QoS management domain and by offering a high level expressivity, the QoSL4BP language enables an easy, flexible and reusable specification of both QoS contracts management and QoS related mechanisms implementation. This language is executed by our ORQOS platform, which cooperates ina non-intrusive way with orchestration engines. Thus, at pre-deployment time, the ORQOS platform performs service planning depending on services QoS offers and on the QoS requirements in QoSL4BPpolicies. At runtime, the QoSL4BP policies make it possible to react to QoS variations and to enact QoS management related mechanisms. Two scenarii, belonging to telecommunications and medical domains, validate our approach. ; L'avènement des architectures orientées service tend à promouvoir un style d'architecture logicielle où des services, exposant des fonctionnalités accessibles à l'aide de protocoles hautement standardisés sont composés avec un couplage lâche. Dans un tel contexte où les services sont aisément amenés à être remplacés ou utilisés par un grand nombre d'utilisateurs, la notion de Qualité de Service (QdS), qui s'intéresse à la qualité de la relation entre un service et ses clients, constitue un enjeu majeur. La QdS regroupe diverses préoccupations telles que la sécurité, la garantie de livraison, la performance (temps de réponse ou accessibilité) ou encore le coût. Bien qu'il existe déjà d'importants travaux autour des compositions de services, qui ont notamment permis l'élaboration du standard BPEL4WS, le problème de la gestion de la QdS dans les compositions de services manque de solution flexible, réutilisable et offrant un degré d'abstraction approprié.L'objectif de cette thèse est de faciliter la gestion de la QdS dans les compositions de services en s'appuyant sur une meilleure séparation des préoccupations. Pour cela nous proposons QoSL4BP, un langage dédié qui permet la spécification de politiques de QdS à l'échelle des compositions de services. Ces politiques gèrent des contraintes et des mécanismes de QdS statiquement et dynamiquement à l'aide d'un ensemble limité de primitives de haut niveau. En encapsulant l'expertise liée au domaine de la gestion de QdS et en offrant une expressivité de haut niveau, le langage QoSL4BP permet une spécification aisée, flexible et réutilisable de la gestion des contrats de QdS et des mécanismes liés à la QdS. Ce langage est mis en œuvre par notre plateforme ORQOS qui coopère de manière non intrusive avec les moteurs d'orchestration. Ainsi, au moment du déploiement d'une composition de services, ORQOS sélectionne les services de la composition, selon leurs offres de QdS et les exigences spécifiées dans les politiques QoSL4BP. A l'exécution, les politiques QoSL4BP permettent de réagir aux variations de QdS et de mettre en œuvre des mécanismes liés à la gestion de QdS. Deux scénarii, appartenant respectivement aux domaines des télécommunications et du médical, permettent de valider l'approche proposée.

AbstractQoS-based service composition enables the development of complex business applications. They are composed of distributed services characterized by QoS attributes representing non-functional characteristics, such as cost, execution time, and reliability. With the proliferation of services on the Internet, more candidates for each component service may be available with different QoS values. Hence, the ones satisfying QoS global constraints required for the application have to be selected. Automated negotiation is adopted to select component services in a dynamic market of services where provided QoS values may vary according to different market strategies. Nevertheless, when dealing with multiple QoS attributes, multiple service providers, and not shared information, it is difficult to guarantee the formal properties of the negotiation outcomes. In the present work, we propose a trade-off negotiation strategy that allows reaching a Pareto-optimal agreement, if it exists. The agreement consists of the QoS values of component services that are the ones selected to provide the complete application. The strategy exploits both the competition, that is due to multiple services providing the same functionality with different QoS values, and the cooperation among the providers of the different component services, that are necessary to meet the required end-to-end QoS constraints.