Supporting Quality of Service properties in BPEL processes is essential to enable Web Service based production workflows. In fact, when implementing a Web Service composition with a BPEL process, appropriate means are needed to express and enforce various QoS properties such as security, reliable messaging, and transactions. In this paper, we present a generic and non-proprietary approach to express QoS properties in BPEL processes using policies. This approach uses XPath, WS-Policy, and the external policy attachment mechanism of WS-PolicyAttachment to enable a separate and non-intrusive specification of both the messaging-level and process-level QoS requirements in BPEL processes. We also present a prototype implementation on top of the Colombo BPEL engine, which supports the enforcement of policies that are attached to BPEL activities.
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