Re: NULLs: theoretical problems?

From: Keith H Duggar <>
Date: Sat, 01 Sep 2007 08:59:58 -0700
Message-ID: <>

Bob Badour wrote:
> Keith Duggar wrote:
> > I'm not trying to have anything. I'm trying to understand what
> > the "write DEF" prescription buys us over say the "Interactive
> > Mathematical Proof System" of Farmer, Guttman, and Thayer that
> > has exactly the property I described that any formula is false
> > if any variable is NULL. Again, I am failing to grasp what the
> > "write DEF" prescription buys us. I would like to understand.
> > KHD
> Error detection. It forces one to acknowledge that one understands the
> attribute can be undefined and that one is ignoring those propositions
> for which it is undefined.

So one kind of error detection it allows is checking that a user understands an attribute can be undefined? How helpful would that be in preventing common query errors? Or does it allow error detection beyond NULL understanding checks?

Thanks for help.

KHD Received on Sat Sep 01 2007 - 17:59:58 CEST

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