Applying Concept Reuse for Adaptive Service Composition

Web Services are gaining acceptance as the predominant standards-based approach to building open distributed systems. Business Process Execution Language (BPEL) allows for the composition of existing Web Services to create higher-level Web Services. There is a need to deliver reliable service compositions with precise Quality of Service (QoS) attributes covering functional correctness, performance and dependability, especially since the current BPEL standard provides limited constructs for specifying exceptional behavior and recovery actions. This chapter presents a language-based approach to transparently adapting BPEL processes to improve reliability. This approach addresses reliability at the business process layer (i.e., the language layer) using a code generator, which weaves fault-tolerant code to the original code and an external proxy. The chapter also explains the software patterns present in this approach. These patterns constitute abstract reusable concepts that will facilitate rapid model-driven development of adaptive service compositions that can be easily configured for a range of situations.