Re: Proposal: 6NF
Date: 6 Oct 2006 06:07:17 -0700
Message-ID: <1160140037.161745.23180_at_i3g2000cwc.googlegroups.com>
Brian Selzer wrote:
> >> Is the empty set a value? Yes, it is. So why can't a null be?
> >
> > Because an empty set is a value and a NULL is not.
> >
>
> Why not?
> The empty set /indicates/ the absence of a value, yet it /is/ a value; a
> null /indicates/ the absence of a value, yet it /isn't/ a value? Why the
> double standard?
The *absence of value* (known as missing data) certainly is not a value
. A value is the output of a function. As a missing data is several
possible outputs there it is NOT a value but several possible value.
The *unpredictability* of a missing data disqualifies it as a value.
The empty set OTOH perfectly qualifies as a value as it is the output of a function that can be defined and predicted. Received on Fri Oct 06 2006 - 15:07:17 CEST