Re: Proposal: 6NF
Date: 6 Oct 2006 05:07:02 -0700
Message-ID: <1160136422.002344.269890_at_m7g2000cwm.googlegroups.com>
Brian Selzer wrote:
> "JOG" <jog_at_cs.nott.ac.uk> wrote in message
> news:1159970386.339044.87090_at_i42g2000cwa.googlegroups.com...
> > Brian Selzer wrote:
> >> "JOG" <jog_at_cs.nott.ac.uk> wrote in message
> >> news:1159954091.119164.155490_at_m73g2000cwd.googlegroups.com...
> >> > All of your points represent a wild goose chase in my eyes Brian. A
> >> > proposition with a NULL in it is no proposition at all. From a logical
> >> > perspective, case closed. A relation tuple with a NULL in it is no
> >> > relation tuple at all. From a mathematical perspective, case closed.
> >> > Trying to invoke the 'kludge perspective' is hardly going to convince a
> >> > theoretical newsgroup.
> >> >
> >>
> >> 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?
Because that is how it is defined. This is not an opinion it is a fact.
"The person with id:1 has NAME:Brian and has AGE:NULL" ...is not a proposition. It is a kludge to squash two propositions into one, representing:
The person with ID:1 has NAME:Brian.
AND
The person with ID:1 has a MISSING/INAPPLICABLE/UNKNOWN: age.
Clearly the value in question is actually "age".
I worry that you do not actually want to get your head round this admittedly subtle issue, but are rather just being polemic. Hopefully not, because from a theory point of view this is all there is to it.
>> > proposition.
> >>
> >> By your reasoning, a proposition with an integer in it is no proposition
> >> at
> >> all; a proposition with a string in it is no proposition at all; a
> >> proposition with a widgit in it is no proposition at all.
> >
> > poppycock. Those are all fine propositions.
> >
> >>
> >> Also, haven't you heard of the existential quantifier?
> >
> > Not in a proposition of fact, absolutely not.
> >
> > This has been explained many times now. A null _indicates_ that there
> > is a missing/unknown/inapplicable value, it is not a value itself. A
> > proposition with a missing/unknown/inapplicable hole is not a
> >
>
> 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?
Wrong, wrong, wrong! The empty set is a value by itself, not an indicator of anything. Any set is a value, regardless of its contents. /Please/ dive into some mathematical text books if you still find this genuinely confusing.
>> >> X, Y, and Z is a perfectly valid construct in FOPL.
> >> For example, if a
> >> schema {X, Y, Z} has X as a key and Z can be null, then the sentence
> >>
> >> EXISTS x (P(x) XOR Q(x))
> >>
> >> where P is defined in terms of X and Y and where Q is defined in terms of
> >
Received on Fri Oct 06 2006 - 14:07:02 CEST