Divergent Hierarchies - revisited (1)

• C++ does not support divergent class hierarchies.

• One alternate is prototype objects with delegation.

• RDB’s can support prototypes and delegation:

• In our example, each dog object belongs to one subclass for color, and simultaneously to another subclass for size.

• That is, a ‘real’ dog object simultaneously belongs to, and inherits from, exactly one of the subclasses in each inheritance tree above.

• The next slide shows (by its messiness) that multiple inheritance is best avoided.

Partition S1:

(BLACK xor WHITE)

(Mutex and exhaustive):

DOG CLASS

Partition S2:

(BIG xor SMALL)

(Mutex and exhaustive):

Black Dog

White Dog

Big Dog

Small Dog

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