Policy-driven middleware for adaptive web services composition

Web services composition is gaining acceptance as a standards-based approach to automate business processes. A key resulting challenge is to ensure adaptive composition enactment to adapt to changing operating conditions such as the failure or QoS degradation of one or more constituent services. However, adaptability is not yet adequately supported by current service composition platforms. Additionally, the adaptation logic is often scattered and tangled with the specification of the base process. Consequently, this negatively impacts maintainability and adaptability. To address these issues, this paper proposes an extensible set of adaptation policies to declaratively specify exception handlers for typical exceptions in service-based business processes. The identified constructs were incorporated into a lightweight service management middleware named Manageable and Adaptive Service Composition (MASC) to transparently enact the adaptation policies and facilitate the monitoring and control of managed services. Several experimental results using a Loan Broker process illustrate the effectiveness of our approach to providing adaptive services.