Inheritance Algorithm
To retrieve a value V for attribute A of an instance object O:
2. If there is a value there for A report that value.
3. Otherwise follow the instance link (no link means failure)
and report the value of A associated with the class.
4. Otherwise follow isa links up the hierarchy until a value V
is found for A or until no more isa links are available.
Fine if your hierarchy is a tree…but what if it’s a directed,