Re: Proposal: 6NF

"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?

>>
>> 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
> proposition.
>

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?

>> 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
>> X, Y, and Z is a perfectly valid construct in FOPL.
>
Received on Fri Oct 06 2006 - 10:32:36 CEST