Analyzing Temporal Constraints for Web Services Composition

Web service composition has become the optimum technique for Service Oriented Architecture applications because it provides a way to obtain value-added services by combining several Web services. One key issue is that service composition must meet user’s deadline requirements. In this paper we focus our attention on modeling and analyzing time-related properties in service composition. A model called extended time Petri net (ETPN) is introduced, in which the temporal constraints are across transitions. The formal definitions of atomic Web service and service composition are proposed based on ETPN. Timestamp state class method is used to analyze the temporal constraints. Some definitions of service composition are presented such as effective path, compatibility, etc. An algorithm is developed to analyze the weak compatibility of two Web services. Furthermore, the approach of service compatibility checking is provided. Finally, a real-life case is given to evaluate our proposal and to demonstrate the applicability of our approach.