Application of Business Process Execution Language to Scientific Workflows

This paper investigates the use of the Business Process Execution Language for Web services (BPEL4WS/ BPEL) for managing scientific workflows. The complexity, unpredictability and inter-dependency of the components in a scientific workflow often demand great flexibility in a workflow-language in order to support; 1) exception handling, 2) recovery from uncertain situations, 3) user interactions to facilitate interactive steering and monitoring, 4) dynamism to adapt to the changing environment, 5) compensation handling to reverse the effects of previous activities that have been abandoned, and 6) flexibility to support dynamic selection of services at runtime and to support changing data requirements. These requirements are illustrated with examples taken from a real scientific workflow; the e-HTPX project for high throughput protein crystallography. In the context of addressing these requirements, the features of the BPEL4WS specification are discussed, which is widely regarded as the de-facto standard for orchestrating Web services for business workflows. An investigation and proposal for the use of the Web services Invocation Framework (WSIF) [38] to extend BPEL is also provided. In summary, by extending BPEL where necessary (in conjunction with standard BPEL features), workflows can be successfully adapted to fulfill all the requirements of complex scientific workflows.