Re: So what's null then if it's not nothing?

Frank Hamersley wrote:
> Jon Heggland wrote:
> > In article <1133894046.516473.27860_at_f14g2000cwb.googlegroups.com>,
> > boston103_at_hotmail.com says...
> >
> >>>>>What do you call the domain { TRUE, UNKNOWN, FALSE }? And by the way,
> >>>>>haven't you argued for ages that names don't matter?
> >>>>
> >>>>Names do not matter, but the number of logical constants does. If
> >>>>it's more than two, then the logic is most certainly not Boolean.
> >>>
> >>>You are quibbling.
> >>
> >>I beg your pardon ? The number of logical constants, not thir names,
> >>is what distinguishes propositional logic from various multivalued
> >>logics, including various breeds of 3VLs.
> >
> > You don't answer my questions; you come up with complete non sequiturs.
> > A domain has a name. The domain consisting of the values { TRUE, FALSE }
> > is called Boolean. There is another domain, consisting of the values {
> > TRUE, UNKNOWN, FALSE }, which I called "3VL Boolean".
>
> The trouble with your definition is that it is nonsensical - more than a
> bit like what Alice encountered!
>
> The root problem is that the "UNKNOWN" (aka NULL) itself is not and
> never will be a member of that or any other domain. Accordingly others
> have called is a "Special" value.
>
> When the attribute value does become known (lets say it is "MAYBE") then
> it is no longer UNKNOWN, it is MAYBE and it is a member of the domain
> (YES, NO, MAYBE) (sic) :-)
>
> [..]
>
> Personally I don't understand why NULL is so hard "to get". But then
> there are lots in IT who don't get it so I should expect this thread
> will rise again in about a years time (assuming it has died in the
> intervening period).
>
> Frank.

Please listen to Frank, for he is wise. 300 posts and climbing - Codd has a lot to answer for with his inclusion of nulls (well, that and his re-imagineering the definition of a mathematical relation) and the confusion they engender in the otherwise great RM. unknowns and logical domains? Just say no. Received on Wed Dec 07 2005 - 15:56:18 CET