1. A service-oriented system for integrating an existing web-based application to form a service to be provided to users, the system comprises: a service inlet for receiving a service request containing an input data set submitted by a user; a service proxy interlace formed by integrating the existing web-based application, for transforming the input data set in the service request submitted by the user into input parameters recognizable by the requested service and loading a model definition document corresponding to the service according to the service request submitted by the user, the model definition document being formed by integrating the existing web-based application; and an execution engine for interacting with an external resource according to the input parameters transformed by the service proxy interface and returning the information obtained from the external resource to the service proxy interface.