Towards runtime discovery, selection and composition of semantic services

Service-orientation is gaining momentum in distributed software applications, mainly because it facilitates interoperability and allows application designers to abstract from underlying implementation technologies. Service composition has been acknowledged as a promising approach to create composite services that are capable of supporting service user needs, possibly by personalising the service delivery through the use of context information or user preferences. In this paper we discuss the challenges of automatic service composition, and present DynamiCoS, which is a novel framework that aims at supporting service composition on demand and at runtime for the benefit of service end-users. We define the DynamiCoS framework based on a service composition life-cycle. Framework mechanisms are introduced to tackle each of the phases and requirements of this life-cycle. Semantic services are used in our framework to enable reasoning on the service requests issued by end users, making it possible to automate service discovery, selection and composition. We validate our framework with a prototype that we have built in order to experiment with the mechanisms we have designed. The prototype was evaluated in a testing environment using some use case scenarios. The results of our evaluation give evidences of the feasibility of our approach to support runtime service composition. We also show the benefits of semantic-based frameworks for service composition, particularly for end-users who will be able to have more control on the service composition process

Rahmenwerk zur integrativen Gestaltung von Services: Modellgetriebene Servicebeschreibung

Die vorliegende Arbeit befasst sich mit der modellgetriebenen Servicebeschreibung, einem Ansatz zur integrativen Beschreibung bzw. Modellierung von Services. Ausgehend von der Prämisse, dass die Natur von Services nur schwer zu erfassen ist und eine Disziplinen-übergreifende Positiv-Definition nicht erreicht werden kann, soll mit dem Ansatz eine Syn-these bisher vorhandener Modellierungsansätze erfolgen. Das Ziel liegt dabei nicht in einem erneuten Versuch, ein vollständiges Modell zur Beschreibung von Services zu entwickeln, sondern vielmehr vorhandene Perspektiven so zu integrieren, dass ein vollständiges Bild als eine Art Mosaik entsteht. Den Kern der Arbeit bildet das Service Modeling Framework. Als Rahmenwerk umfasst es Anforderungen und Restriktionen für die Arbeit mit unter-schiedlichen Servicemodellen, definiert Methoden zur Integration und bietet Werkzeuge, mit deren Hilfe die darin enthaltenen Konzepte umgesetzt werden. Ziel der Konstruktion des Rahmenwerks ist es Nutzer in die Lage zu versetzen mittels mo-dellgetriebener Verfahren eine Zusammenführung von Modellen zu ermöglichen. Auf Basis einer fachlichen, nicht nur syntaktischen Beschreibung von Beziehungen zwischen Model-len und Modellelementen sollen Zusammenhänge modelliert werden, die einen Informati-onsaustausch zwischen Modellen realisieren. Dadurch werden Abhängigkeiten zwischen Modellen explizit formuliert oder aber die Entwicklung neuer Modelle auf Basis bereits bestehender Modelle vorangetrieben. Der Beitrag dieser Arbeit besteht in der Erarbeitung der notwendigen Konzepte und in der Bereitstellung geeigneter Verfahren sowie Werkzeugen zur Umsetzung. Insbesondere stellt diese Arbeit einen Metamodell-basierten Ansatz zur Verfügung, mit dem Modelle über ein Domänen-neutrales Basismetamodell zueinander in Beziehung gesetzt werden können. Zugehörige Werkzeuge, wie Editoren, zeigen eine prototypische Umsetzbarkeit

Web service composition : architecture, frameworks, and techniques

OASIS defines Service Oriented Architecture (SOA) as a paradigm for organizing and utilizing distributed capabilities that may be under the control of different ownership domains. One approach to realize SOA is Web services. A Web service is a software system that has a machine processable Web Services Description Language (WSDL) interface; other systems interact with it using SOAP messages in a manner prescribed by its description. Descriptions enable Web services to be discovered, used by other Web services, and composed into new Web services. Composition is a mechanism for rapid creation of new Web services by reusing existing ones. Web services have functional, behavioral, semantic, and non-functional characteristics. These characteristics have to be considered for composition, as they provide essential information about the services. In order to compose Web services with these characteristics, they have to be described appropriately. However, the existing techniques do not consider all these aspects together for description and composition. This thesis proposes a business model, also referred to as architecture, a description framework, and a composition framework for Web service composition. Techniques for matching, categorizing, and assembling the composite services are also proposed as a part of the composition framework. The architecture, frameworks, and techniques describe, discover, manipulate, and compose Web services by taking into account all their characteristics. The standard Web service business model is extended by the proposed business model to support Web service composition. In the model, based on their demand, the requested Web services are composed by the Web service composer. In the proposed architecture, Web services are described using the description framework languages. The proposed framework combines Semantic Annotations for WSDL and XML Schema (SAWSDL) for functional and semantic description, Message Sequence Charts (MSC) for behavioral description, and a simple and new Non Functional Specification Language (NFSL) for the non-functional properties description of Web services. It uses Higher Order Logic (HOL) for formalizing and integrating the three languages. The role of Web service composer in the architecture is realized by the composition framework. It essentially defines the architecture of the composer. In this framework, matchmaking, categorization, and assembly techniques are used to create the requested composite service. These techniques manipulate the Web services at HOL-level. The formal matchmaking technique discovers the primitive Web services by using a HOL theorem prover. The categorization and the assembly techniques manipulate the matched services and orchestrate the composite service. The concepts of the model, frameworks, and techniques are implemented, and their working is illustrated using case studies. Prototypes of the model's components (extended registry and extended requester) and the composition framework are developed, and their performance is analyzed. Case studies to illustrate the description and the composition frameworks are also presente