COOL is a hybrid of features from many different OOP systems as
well as new ideas. For example, object encapsulation
concepts are similar to those in Smalltalk, and
the Common Lisp Object System (CLOS) provides the basis
for multiple inheritance rules. A mixture of
ideas from Smalltalk, CLOS and other systems form the foundation
of messages. Section 8.1 explains an important contrast
between the terms method and message-handler
in CLIPS.