Timing Constraints Specification and Verification for Web Service Compositions

Web service composition is an emerging paradigm for enabling application integration within and across organizational boundaries. Since most business processes exist in temporal context in real world, and the candidate partners in Web service compositions have complex interactions, timing constraints satisfiability verification for Web service compositions becomes increasingly important to build efficient and effective business processes based on Web services. In this paper, we present an approach to specify and verify timing constraints satisfiability for the compositions of Web services workflow based on BPEL4WS(Business Process Execution Language for Web Services). By using timing constraints annotation layers, a BPEL4WS model can be extended with timing constraint information. The pair of an underlying BPEL4WS model and a timing constraint annotation layer can be transformed to corresponding TPPN (Timed Predicate Petri-net) model to verify automatically timing constraint satisfiability for a business process. The method allows us to add conveniently timing constraints information to a business process model,and find whether a process is schedulable and which activities in the process are not schedulable under the consideration of timing constraints without actual execution based on its specification. The paper describes how to specify timing constraints for compositions of Web services workflow, and how to determine whether the specification satisfies its timing constraints.