Policy-Based Customization and Corrective Adaptation of Composite Web Services

Abstract

Due to the typical long-running character of business processes, it is often desirable to be able to change a running process. Common scenarios include the occurrence of faults, the change of business requirements and company policies that need to be reflected in running process instances. Hence, running process instances often need to be adapted to keep fulfilling the functional and QoS requirements of their dynamic business environment. However, current process orchestration engines do not provide the flexibility and dynamism needed to support ad-hoc changes (e.g., add, shift or delete activities) to a pre-defined service flow in order to deal with an exceptional situation that may occur during process execution. In this paper, we advocate a policy-based framework to manage customization and corrective adaptation of Web services in a controlled and reliable way. WS-Policy4MASC language is used to define process-level adaptation requirements. The latter are enforced by MASC (Manageable and Adaptable Service Compositions) middleware both at creation time and during an instance’s lifecycle. MASC middleware can be deployed as a transparent and configurable add-on to a BPEL engine to support the detection of a need to adapt and manage the adaptation. This paper also presents MASC middleware prototype implementation and some experimental results showing its viability and scalability. Several experimental results using a Stock Trading process illustrate the usefulness and effectiveness of our approach to providing adaptive services.