Fault Tolerance in Automatic Semantic Web Service Composition based on QoS-awareness Using BTSC-DFS Algorithm

Quality-of-Service (QoS)-aware web service composition is very important in integrating individual services with respect to the functional and nonfunctional requirements. Despite the large number of candidate services, automation of the combination is essential in order to provide a good combination of service. Although many of the existing methods offer a solution that is optimal, most of them have little flexibility. In some cases, the compound service components fail, so the combination algorithm has to run again to find another optimal solution. Also in many situations, users prefer to have several alternative solutions. Therefore, providing a top-k service composition according to their QoS is more desirable. Because web services are unreliable, also since providing the transactional support in execution of a service composition is an important design requirement; so in this research, a fault management procedure is implemented to ensure the transaction execution of the service combinations. This procedure in the event of service failure undo the impact of this service by calling the equivalent service.The proposed method encounters these three issues: 1) the semantic selection of services; 2) QoS-aware web service composition with the top-k solution; and 3) fault-handling/recovery procedure. In the proposed method, ontology concept ranking algorithm is used in service selection, and top-k method is employed to solve service combination. Error handling procedure will then be reviewed and designed to ensure the transactional execution of the service composition. The evaluation results show that the proposed method not only finds optimal solutions but also can provide alternative solutions with optimal QoS.