To mine the process model including multi-concurrent 2-loops of triangles in incomplete logs, an AlphaMatch algorithm based on extended Alpha algorithm was proposed. Two activities in triangle structure could be correctly matched in 2-loops of triangles by AlphaMatch in the log without repeated activity sequence, thus the process model with multi-concurrent 2-loops of triangles could be mined. Firstly, the activities in 2-loops of triangles were divided into two categories according to the number of activities. Then, a matrix of head and tail position of the activities was constructed to match the two categories and a footprint matrix was constructed to show the relationship between activities. Finally, a large number of experiments were carried out on ProM platform from model correctness, mining efficiency, fitness and precison. Experimental results show that the Petri net model including multi-concurrent 2-loops of triangles can be mined efficiently by the proposed algorithm.

To improve the searching speed and get optimal services compositions on large scale of semantic Web services, a quick composition approach based on service cluster and Quality of Service (QoS) was proposed. Using the pre-built service clusters, it could quickly get the candidate service set with the effectively reduced searching space and semantic comparison complexity. It could obtain more optimal compositions by filtering service with the dynamically determined threshold based on the best composition QoS in the process of composition. It adopted an effective redundancy processing method to ensure minimum redundant services were used in the composition, and a service cluster internal filtering method was used to limit the number of candidate services, that solved the operation overtime problems caused by too many compositions. The results of experiments performed on large scale service storage illustrate that the searching speed is improved dozens of times than common methods, and the effectiveness of service filtering and redundancy processing is remarkable, so that the approach can quickly get multiple QoS optimal and non-redundant service compositions, and perform well on deep hierarchy composition in service storage of millions level.

In order to reduce the search space and improve the efficiency of service discovery, the concept of service cluster was put forward. Web services with the same or similar functions were encapsulated as a service cluster. The request/response schema based on service clusters was constructed. The formal definition of service cluster, the architecture and an algorithm to discover the optimal Web service in the service clusters schema were presented. The simulation experiment was conducted on 10000 Web services. The discovery time and rediscovery time under service clusters schema were less than 600ms when the number of service clusters was no more than 1000. However, the above time was more than 900ms in the current service response schema. The efficiency is greatly increased in discovering services under service clusters schema, and the rediscovery time is also greatly decreased.