Model-driven performability analysis of composite web services

Web services are the building blocks of the emerging computing paradigm based on service-oriented architectures (SOAs). A web service is a self-describing, open component that supports rapid composition of distributed applications. In a SOA context, service providers are strategically interested both to predict and describe the QoS of the offered services. This paper introduces a model-driven approach to automatically predict and describe the QoS of composite web services specified by use of the Business Process Execution Language for Web Services. The paper is founded on a lightweight QoS-oriented extension of the WSDL and specifically addresses the QoS in terms of the performability attribute, which defines a combined measure of performance and reliability. The proposed approach is illustrated by use of an example application that shows how the performability analysis may lead to predictions that do not correspond to those obtained by approaches that only consider the performance attribute.