组合服务选择中的服务QoS反演

QoS-aware inversion for composite service selection

针对组合服务选择中原子服务的服务质量（QoS）未知的情形，提出了服务QoS的反向计算问题，通过对问题的详细分析将其转化为计算原子服务归一化QoS的问题，进一步提出了根据组合服务的QoS反向计算各原子服务归一化的QoS的反演算法，使得在原子服务QoS未知的情况下基于QoS进行组合服务选择成为可能，并在反演算法的基础上提出了支持服务QoS变化的动态调整策略。仿真实验表明，通过反演算法计算出的原子服务9-3一化的QoS能够逼近其真实值，并且当服务的QoS变化时，动态调整策略也能及时地做出调整，对原子服务归一化的QoS进行更新，增强了服务选择的准确性。

In order to solve the problem that the quality of service （QoS） of a component service is unknown during service selection for a composite service, this paper proposes the concept of QoS-aware reverse calculation, i. e. the problem can be converted into the calculation of the normalized QoS of component services, through a detailed anal- ysis. Based on this, an inversion algorithm which calculates the normalized QoS of component services according to the QoS of the composite services is put forward. The inversion algorithm makes the QoS-aware service selection possible when the QoS of the component services is unknown. Based on the inversion algorithm, a dynamic strategy to support the change of the QoS of the component services is also proposed. The experimental results show that the normalized QoS of the component services calculated by the algorithm can approximate the true value. If the quality of services changes, the dynamic strategy can update the normalized QoS dynamically, which enhances the accuracy of the service selection.