Abstract: A generalized stochastic colored Petri net(GSCPN) and a Web service model based on GSCPN were pro- posed. QoS and data representations were realized in this model. Web service composition algorithms based on GSCPNs were proposed. A hierarchical method for GSCPN was proposed for reducing the complexity of a Web service model and mitigating the state explosion problem partly. Properties of composition operations were analyzed. Approaches of analy- zing properties and QoS of the model were investigated.

Key words: Petri net, Web service, Scrvicc composition, Modeling