Re: NULLs: theoretical problems?
From: Jon Heggland <jon.heggland_at_idi.ntnu.no>
Date: Fri, 31 Aug 2007 10:44:13 +0200
Message-ID: <fb8kd7$r2k$1_at_orkan.itea.ntnu.no>
Date: Fri, 31 Aug 2007 10:44:13 +0200
Message-ID: <fb8kd7$r2k$1_at_orkan.itea.ntnu.no>
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?
-- JonReceived on Fri Aug 31 2007 - 10:44:13 CEST