1. A method to represent in UML resources and external data manipulated by programs of a software application to be coded in a procedural language, said method comprising: a developer creating an initial UML class diagram modelizing the software application and extending an initial class diagram by: applying a new “Data Object” stereotype to data definition classes in the initial UML class diagram which represent logical data; applying a new “Program” stereotype to the corresponding class operations which represent programs in the initial UML class diagram; for each parameter of each “Program” stereotyped class operation that represents a Resource manipulated by the program in the initial UML class diagram, creating a new UML class; applying a new “Resource” stereotype to this new class; linking the new class to the Data Object class that is used as a type for the given parameter in the initial UML; applying a “resourceIsStructured” stereotype to the link; changing the parameter type to use the newly created Resource class instead of the Data Object class; the other parameters of each “Program” stereotyped class operation that do not represent a Resource manipulated by the program in the initial UML class diagram, represent external data in the extended class diagram.