Re: NULLs: theoretical problems?

From: Jon Heggland <>
Date: Fri, 31 Aug 2007 10:44:13 +0200
Message-ID: <fb8kd7$r2k$>

Quoth Keith H Duggar:
> 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.

In this system, how can you check whether a given variable actually is NULL or not?

Received on Fri Aug 31 2007 - 10:44:13 CEST

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