1. A method for managing CAD data by using a CAD-data processing function being capable of processing a predetermined type of CAD data, comprising the steps of: (a) receiving a manipulation input designating CAD data of said predetermined type; (b) generating a processing request corresponding to said manipulation input and being directed to said CAD-data processing function; and (c) executing processing defined in an interface function in conjunction with said CAD-data processing function, where said interface function is predefined corresponding to said processing request.