Re: Does Codd's view of a relational database differ from that ofDate&Darwin?[M.Gittens]

From: Mikito Harakiri <>
Date: 7 Jul 2005 09:11:23 -0700
Message-ID: <>

Jon Heggland wrote:
> Because it isn't. Temperature is not the union of double, double and
> double, or even of fahrenheit, celsius and kelvin. Point is not the
> union of cartesian points and polar points. It does not even make sense
> to speak of such a union, because the set of cartesian points and the
> set of polar points is the same set---the set of 2D points. (0,4) and
> (4,90) is the same point, just like 14 and 0xE is the same int.

User defined types present rather archaic approach to units. Modern approach is symbolic manipulation

(This is well known technique, BTW that has been posted many times on sci.math). Received on Thu Jul 07 2005 - 18:11:23 CEST

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