Inheritance Taxonomy
An object's interface (try to forget the way Java has co-opted the term for its own ends) is the set of messages to which it will respond. Thus, interface inheritance is the declaration that one class will respond to the same set of messages as another. This is the cornerstone of polymorphism: two objects that respond to a common set of messages (having a common interface) can be substitued for each other at compile- or run-time, allowing for more dynamic and flexible programming. →