With the development of web service technology, composing services to meet needs of customers has become an inevitable trend. Web services on the internet are distributed, heterogeneous, autonomous and dynamic, which leads to two kinds of uncertainty of web services
Uncertainty of web services refers to the uncertain results of invoking services and the uncertain QoS (Quality of Services) values, which are hard to precisely predict and affect the process of service composition. Therefore, when taking into account the uncertain and dynamic nature of real-world cases, the following considerations have practical significance for reliable services composition: how to compose services based on implicit knowledge of business logics and how to model uncertain QoS values to ensure that composite services have higher QoS.