Re: How to cope with missing values - NULLS?

"Peter Koch Larsen" <pkl_at_mailme.dk> wrote in message news:61c84197.0304220818.3050fbdf_at_posting.google.com... [ snip ]
> There is not much of a difference the way I look at it and it really
> bugs down to how you feel the "=" operator should work.

Indeed it does really boil down to how equality works..

Quite simply I take it as a axiom that

    x = x
 for all possiable values x

if you want to break this by introducing something that is not a value, then be my guest, but don't expect many others to follow you.

> One of my thoughts have been that it might be a good idea to introduce
> an equivalence operator (we could call it "~") behaving the same way
> as your operator does (UNK ~UNK = TRUE); I've never heard this idea
> proposed anywhere else.

Indeed you could, but please use it as a founding operator of your own system of mathematics and stop bothering us with such stuff.

If you are interested in what (some of) the rest of the world thinks about equality, try following the link Costin gave out recently

    http://www.nuprl.org/html/NaiveTypeTheoryPreface.html

Regards
Paul Vernon
Business Intelligence, IBM Global Services Received on Tue Apr 22 2003 - 19:27:43 CEST