摘要：Service composition is widely applied in different applications. One key issue is how to model and analyze time-related properties for service composition. A model called service composition time-constrained Petri Net ( SCT-Net ) is proposed in the paper, which is capable of capturing time behavior of services accurately. The basic relationships, priority and preemption between services are characterized, meanwhile the transaction properties of service are also considered. In order to reduce the state space of model, we propose four simplification schemas which can maintain structural feature and time delay of SCT-Net , a theorem is given to explain the rational of simplification schemas. We present the concept of the greatest concurrent set and analyze the consistency of overtime handling based on the state space of the model. Finally, a heuristic algorithm for schedule computation is created and the experiments are given to explain the feasibility of our method
关键词：Web service;Petri Net;priority;transaction;state space
