QoS-driven web service composition with inter service conflicts

Web service composition provides a way to build value-added services and web applications by integrating and composing existing web services. In a two-stage approach for web service composition, an abstract specification is synthesized in the first phase and an executable composition process is generated in the second phase by selecting and binding a concrete web service for each abstract task. However, the selection of a web service for one task is not a stand-alone operation, as there may be compatibility conflicts between this service and services chosen for other tasks. This paper gives a method for dynamic web service selection in the presence of inter service dependencies and conflicts. Firstly, a method based on Integer Programming is discussed to implement the process of dynamic service selection. Then, inter service conflicts are explored and expressed formally, which are accommodated into the IP-based method. By combing domain specific service conflicts into a two-stage approach, the method in this paper provides a united approach for dynamic service selection that can integrate both QoS constraints and other domain specific constraints. Experiments show that this method is effective and efficient.