A class that provides some but not all of the 
implementation for a virtual base class is often called 
mixin. Derivation done just for the purpose of redefining 
the virtual functions in the base classes is often called 
mixin inheritance. Mixin classes typically don't share 
common bases..

Mixin is a class that does not implement any method but are 
in fact has only pure virtual methods. The implementor 
decides the logic for these methods.

The term mixin were originally explored in the Lisp 
language In C++, the term has been used to describe classes 
in a particular (multiple) inheritance arrangement:

As superclasses of a single class that themselves have a 
common virtual base
class .

We would like to specify an extension without pre-
determining what exactly it can extend. This is equivalent 
to specifying a subclass while leaving its superclass as a 
parameter to be determined later. The benefit is that a 
single class can be used to express an incremental 
extension, valid for a variety of classes.

Mixin is a class that does not implement any method but are 
in fact has only pure virtual methods. The implementor 
decides the logic for these methods.

The term mixin were originally explored in the Lisp 
language In C++, the term has been used to describe classes 
in a particular (multiple) inheritance arrangement:

As superclasses of a single class that themselves have a 
common virtual base
class .

We would like to specify an extension without pre-
determining what exactly it can extend. This is equivalent 
to specifying a subclass while leaving its superclass as a 
parameter to be determined later. The benefit is that a 
single class can be used to express an incremental 
extension, valid for a variety of classes.