We propose the PREvent framework, which is a system that integrates event-based monitoring, prediction of SLA violations using machine learning techniques, and automated runtime prevention of those violations by triggering adaptation actions in service compositions. PREvent improves on related work in that it can be used to prevent violations ex ante, before they have negatively impacted the provider's SLAs. We explain PREvent in detail and show the impact on SLA violations based on a case study.

Service-Oriented Computing has recently received a lot of attention from both academia and industry. However, current service-oriented solutions are often not as dynamic and adaptable as intended because the publish-find-bind-execute cycle of the Service-Oriented Architecture triangle is not entirely realized. In this paper, we highlight some issues of current web service technologies, with a special emphasis on service metadata, Quality of Service, service querying, dynamic binding, and service mediation. Then, we present the Vienna Runtime Environment for Service-Oriented Computing (VRESCo) that addresses these issues. We give a detailed description of the different aspects by focusing on service querying and service mediation. Finally, we present a performance evaluation of the different components, together with an end-to-end evaluation to show the applicability and usefulness of our system.

Since the Internet of Services (IoS) is becoming reality, there is an inherent need for novel service selection mechanisms, which work in spite of large numbers of alternative services and take the user-centric nature of services in the IoS into account. One way to do this is to incorporate feedback from previous service users. However, practical issues such as trust aspects, interaction contexts or synonymous feedbacks have to be taken into account. In this paper we discuss a service selection mechanism which makes use of structured and unstructured feedback to capture the Quality of Experience that services have provided in the past. We have implemented our approach within the SOA runtime VRESCO, where we use freeform tags for unstructured and numerical ratings for structured user feedback. We discuss the general process of feedback-based service selection, and explain how the problems described above can be tackled. We conclude the paper with an illustrative case study and discussion of the presented ideas.

A simple and effective composition of software services into higher-level composite services is still a very challenging task. Especially in enterprise environments, quality of service (QoS) concerns play a major role when building software systems following the service-oriented architecture (SOA) paradigm. Inthis paper we present a composition approach based on a domain-specific language(DSL) for specifying functional requirements of services and the expected QoS inform of constraint hierarchies by leveraging hard and soft constraints. Acomposition runtime will resolve the user's constraints to find an optimize dcomposition semi-automatically. To this end we leverage data flow analysis to generate a structured composition model and use two different techniques for the optimization, a constraint programming and an integer programming approach.

Software as a Service (SaaS) and the possibility to compose Web services provisioned over the Internet are important assets for a service-oriented architecture (SOA). However, the complexity and time for developing and provisioning a composite service is very high and it is generally an error-prone task. In this paper we address these issues by describing a semi-automated "Composition as a Service'' (CaaS) approach combined with a domain-specific language called VCL (Vienna composition language). The proposed approach facilitates rapid development and provisioning of composite services by specifying what to compose in a constraint-hierarchy based way using VCL. Invoking the composition service triggers the composition process and upon success the newly composed service is immediately deployed and available. This solution requires no client-side composition infrastructure because it is transparently encapsulated in the CaaS infrastructure.

In general, provenance of electronic data represents an important issue in information systems. So far, service-oriented computing research has mainly focused on provenance of data. However, service provenance also plays a central role since service providers and consumers want to be aware of the service's origin and history. In this paper, we present an approach for service provenance that builds on service metadata and various service runtime events. In addition, access control mechanisms are implemented to restrict access to this information. Besides being able to query and subscribe to provenance information, provenance graphs can be used to illustrate the history of services. We give some usage examples of service provenance and show how our approach was integrated into the VRESCo Web service runtime environment.

Developing cross-organizational business processes is a tedious task. The partners have to agree on a common data format and meaning as well as on the Quality of Service (QoS) requirements each partner has to fulfill. The QoS requirements are typically described using Service Level Agreements (SLAs) among the partners. In this paper, we propose a top-down modeling approach for Web service based business processes to capture the functional and non-functional aspects using a choreography language (WS-CDL) which describes the message interactions among the participants. The choreography is annotated with SLAs for the different partners. For each partner in the process, an orchestration (in WS-BPEL) and the necessary Web service templates are automatically generated. Additionally, the Service Level Objectives (SLOs) from the partner SLAs are automatically translated into policies which can then be enforced by a BPEL engine during execution.

The publish/subscribe style is an emerging paradigm for the construction of loosely coupled systems. Yet, the verification of such systems remains difficult. We have constructed a framework called RAY for testing publish/subscribe applications. This framework is implemented as an Eclipse plug-in. In this paper, we present the detailed architecture of RAY, as well as the interaction with its supporting components. In addition to the presented architecture for a testing framework for publish/subscribe applications, the contribution of this paper includes the experience gained during the development of this framework