Classes seen as modules

A class, seen as a module, is characterized by the following features (we assume that no instance variable is public):

• exported services: the public methods, i.e., the methods visible outside the class;
• interface: the headers of the public methods;
• imported services: other methods or classes used to realize the representation of the objects and of the methods of the class;
• internal structure: representation of the objects and realization of the methods of the class.

Note: The abstraction on objects makes use of the abstraction on operations.