WS-Policy: On Conditional and Custom Assertions

Today, Web services play a dominant role in Enterprise Application Integration (EAI) and for realizing Service Oriented Architectures (SOA), which define the architectural foundation for various kinds of distributed applications. In many business domains, Web services must exhibit quality attributes such as robustness, security, and maintainability. As a consequence, there is a high demand to develop Web services with Quality of Service (QoS) properties. Several specifications of the WS-* family, e.g. WS-Security and WS-Reliable Messaging, aim at simplifying the development and deployment of QoS-aware Web services. Although these approaches cover some typical application scenarios, their expressivity and flexibility are limited by the underlying WS-Policy framework. This paper proposes the syntax and semantics of a new WS-Policy operator that enables the introduction of conditional assertions. Secondly, a framework for managing different types of custom assertions is presented. Finally, this paper describes a proof of concept implementation demonstrating the practical feasibility of both extensions.