# Re: NULLs: theoretical problems?

From: Keith H Duggar <duggar_at_alum.mit.edu>

Date: Sat, 01 Sep 2007 08:43:29 -0700

Message-ID: <1188661409.809212.152280_at_g4g2000hsf.googlegroups.com>

Date: Sat, 01 Sep 2007 08:43:29 -0700

Message-ID: <1188661409.809212.152280_at_g4g2000hsf.googlegroups.com>

Jon Heggland 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.
**>
**> In this system, how can you check whether a given variable actually is
**> NULL or not?
*

**KHD
**
Received on Sat Sep 01 2007 - 17:43:29 CEST