Middleware for Service Oriented Computing 

Abstract: In service-oriented systems, Quality of Service represents an important issue which is often considered when selecting and composing services. For receiving up-to-date information, non-functional properties such as response time or availability can be continuously monitored using server- or clientside approaches. However, both approaches have strengths and weaknesses. In this paper, we present a framework that combines the advantages of client- and server-side QoS monitoring. It builds on event processing to inform interested subscribers of current QoS values and possible violations of Service Level Agreements. These events can trigger adaptive behavior such as hosting new service instances if the QoS is not as desired. We describe our QoS monitoring approach in detail, show how it was integrated into the VRESCo service runtime environment, and evaluate the accuracy of the presented monitoring techniques.

Abstract: Self-Healing is an emerging exigence for Information Systems where processes are more and more complicated and where many autonomous actors are involved. Self-healing mechanisms can be viewed as a set of automatic recovery actions fired at run-time according to the detected fault. These actions can be at infrastructure level (i.e., transparentl to the process), or they can be defined in the workflow model and executed by the workflow engine. Standard recovery mechanisms provided by Ws-BPEL are not enough to implement with reasonable effort lots of suitable recovery actions. The aim of this paper is to present a Self-Healing plug-in for a Ws-BPEL engine that enhances the ability of a standard engine to provide process-based recovery actions.

Abstract: Mobile data services in combination with profluent Web services are seemingly the path breaking domain in current information systems research. In mobile Web services sphere, resource constrained mobile terminals are used as both Web services clients and providers. While service delivery and management from Mobile Host are technically feasible, the ability to provide proper quality of service (QoS) and discovery mechanisms for the huge number of services possible with Mobile Hosts is observed to be very critical. We have studied the security, scalability and discovery aspects of the mobile Web services and the analysis has identified the necessity of a mediation framework. This paper summarizes our QoS and discovery research and discusses the realization details and features of our enterprise service bus technology based integration framework for mobile Web service provisioning.

Abstract: Service-Oriented Architectures (SOA) are built as compositions of inter-organizational services. These services are deployed and published by providers who are responsible for provisioning the services with sufficient resources. However, even though services are implemented by technologies providing a wide range of adaptation related features, such as configurable component models and communication infrastructures, state-of-the-art approaches to adaptive SOA systems do not provide principled solutions to exploit application layer adaptation mechanisms.Our technology-agnostic adaptation middleware has been designed for integrating and exploiting technology-specific adaptation technologies and mechanisms. In this paper, we describe how this middleware can support a cross-layer adaptation of SOA systems. In particular, we focus on the server-side perspective of SOA, and we show that our middleware is able to exploit both service interface and application layers technologies for supporting a coordinated adaptation of both layers.