中文摘要：

针对响应时间，通过选择、调用合适的成员Web服务，对组合Web服务的QoS进行优化．该优化方法基于用户的视角，将组合Web服务运行时用户一次等待周期中需要执行的所有任务作为一个整体进行调度；同时根据组合Web服务流程的不同环节中用户对等待时间的不同敏感度，设置调度参数，降低关键环节超时的风险．实验表明，此方法可以有效地优化组合Web服务的响应时间，提高用户的满意度和QoS．

英文摘要：

Web services technology enables integration of heterogeneous software by encapsulating them into Web services, and building new applications through this way. In addition to the necessary functions, the composite Web services should provide the quality of service （QoS） needed by the users. Response time is one of the important attributes of QoS. The response time of composite Web services is hard to compute because of the loop, conditional selection and concurrent structures in its execution processes. Aiming at composite Web services response time, an optimization method by selecting and invoking appropriate component Web services is proposed in this paper. From user＇s perspectives, this optimization method considers all the tasks＇ response time to be executed in one user-waiting-period as a whole when selecting Web services; and according to the different user-sensitivity-levels in the execution process of a composite service, this optimization method adopts different Web services selection schemes to reduce the risk of overtime for critical points in the process. Experiment results show this method effectively optimizes the response time of composite Web services, improves users＇ satisfaction and services＇ QoS.