A descendent of a class C is any class that inherits directly or indirectly for C, including C itself. Proper descendent of C is a descendent other than C itself. A such that C is a proper descendant of A. A instance of the heir isa instance of the parent, but not conversely. The text of the heir will always mention the parent, but not conversely. Invariant Inheritance rule The invariant property of a class is a boolean AND of the assertions appearing in its invariant clause and of the invariant properties of its parents.
Polymorphism means the ability to take several forms.
In OO Development, a variable or data member has the ability at runtime to become attached to objects of different types, all controlled by static declaration. Also possible to write type conforming feature calls from a polymorphic entity. Type Consistency Inheritance is consistent with type system. Allows combination of static typing and dynamic binding. Decentralization software architecture.