How does implementation inheritance differ from behavior subtyping?
Implementation inheritance allows a subclass to inherit both fields and methods from a super-class. Behavior subtyping allows a subtype to inherit methods defined for a super-type.
What are some major issues associated with implementation inheritance?
Implementation inheritance is problematic because sometimes, the subclass may not want to inherit the fields from a super-class even when it makes logical sense to define the parent-child relationship. As demonstrated from the square-rectangle problem, a subclass may be more restrictive and take away features rather than adding new functionality on top of the super-class. Second, implementation inheritance suffers from the fragile base class issue, for which changes to the super-class may unintentionally modify the behavior of the subclass...
