7. The service-oriented system according to claim 6 , wherein the meta-model used for integrating the existing web-based application comprises at least one of: a service definition that acts as a root node of the meta-model, has a service name, an input message link name and an output message link name, and contains a number of pages and link elements; a page definition for describing a input message, a output message, a URL for accessing it and a security and session setting, which contained in the page; an input message definition for defining data structure of the input data, so as to represent the input data of the existing web-based application as the input parameters of the service to be transformed; at least one output message definition for defining data structure of output data with a explicit business meaning for the user; and a page link definition for determining a flow of page transferring, including source page name, destination page name, output message name of the source page and input message name of the destination page, so as to enable the execution engine to proceed along the page link.
7. The service-oriented system according to claim 6 , wherein the meta-model used for integrating the existing web-based application comprises at least one of: a service definition that acts as a root node of the meta-model, has a service name, an input message link name and an output message link name, and contains a number of pages and link elements; a page definition for describing a input message, a output message, a URL for accessing it and a security and session setting, which contained in the page; an input message definition for defining data structure of the input data, so as to represent the input data of the existing web-based application as the input parameters of the service to be transformed; at least one output message definition for defining data structure of output data with a explicit business meaning for the user; and a page link definition for determining a flow of page transferring, including source page name, destination page name, output message name of the source page and input message name of the destination page, so as to enable the execution engine to proceed along the page link. 8. The service-oriented system according to claim 7 , wherein the input message definition and the output message definition further comprises a simple variable type definition and a complex variable type definition, wherein the complex variable type contains the simple variable type or is embedded in another complex variable type.