To receive an offer of a new function without modification of a function of a client, even if there is a modification of a function of a network service.

A management server 12 transmits a service function format 32, which corresponds to a desired service, to a client 10. A function format display part 22 of the client 10 displays a service providing screen, based on the function format. Parameters, which are in response to data, are sent to the management server 12, after an operator inputs desired data through this window. A service control part 30 of the management server 12 sends out the parameters sent to a server 14 via a server control part 36. There is no need for the client to add any function, because the management server 12 expresses a change in a service function format, which can be interpreted by the client 10, and sends out to the client, even if there is a modification of the function of the service in the server 14.