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From: bpe@brunix (Page Elmore)
Newsgroups: comp.lang.c++,comp.lang.eiffel,comp.lang.smalltalk
Subject: Re: Use of inheritance for classification?
Keywords: metrics, oop
Message-ID: <6365@brunix.UUCP>
Date: 14 May 89 01:04:07 GMT
References: <30582@apple.Apple.COM>
Sender: news@brunix.UUCP
Reply-To: bpe@brown.cs.edu (Page Elmore)
Organization: Brown University Department of Computer Science
Lines: 17


I do not think that inheritence is ever classification: it is specialization.
This misconception will cause you lots of trouble when you attempt to define
a class hierarchy. Classification implies something like:

	Type Car
		color:Red, Blue, Grey, Black, White, etc.
	   |
	   |
	   |
	Type Honda CRX (inherits from Car)
		color: Red, Black

Thus you attempt to constrain the value class of the color attribute, causing
no end of trouble code which attempts to use a Honda CRX in place of a Car.

Page Elmore