Path: utzoo!attcan!uunet!steinmetz!phecda!halvers
From: halvers@phecda.steinmetz (Pete Halverson)
Newsgroups: comp.lang.misc
Subject: Re: object oriented design decision
Message-ID: <12636@steinmetz.ge.com>
Date: 20 Nov 88 19:53:43 GMT
References: <4086@enea.se> <11522@cup.portal.com>
Sender: news@steinmetz.ge.com
Reply-To: halverson@crd.ge.com (Pete Halverson)
Lines: 12

From my experience, multiple inheritence seems to be most useful when
you're trying to represent characteristics that are somehow orthogonal,
i.e. land vehicles vs. sea vehicles, motorized vs. non-motorized, military
vs. commercial.  Single-inheritance-only schemes require you to define a
separate class for each combination (i.e. Motorized-Military-LandVehicle,
NonMotorized-Commercial-SeaVehicle).   If you have many dimensions and many
subclasses, the resulting cross-product is going to get real nasty, real
fast. 

Not to say these kinds of systems aren't complex (I'm currently in the
midst of trying to decipher the Symbolics window class structure) but
multiple inheritance can at least directly represent these orthogonalities.