Object-Orientation FAQ

There are many alternatives in OO.  Emerald/Jade ([Black 86] and [Raj 89])
provides one, where inheritance is replaced with a roughly equivalent form
where reuse occurs at a finer degree of granularity - method and instance
variables - with subtype polymorphism making up the difference.

CLOS [Kim 89, ch 4] has a looser coupling of methods to classes and doesn't
distinguish a receiver, but packages can help make up the difference.

Object Specialization [Sciore 89] is an example of a hybrid approach between
delegation and classical systems, where parent classes have an extra level
of indirection and inheritance hierarchies are specified on a per object/class
basis.