Re: Proposal: 6NF

On Oct 9, 2:56 pm, "dawn" <dawnwolth..._at_gmail.com> wrote:
> J M Davitt wrote:
> > Jan Hidders wrote:
> > > J M Davitt schreef:
>
> > >>dawn wrote:
>
> > >>>Given the definition of NULL that I typically use (with non-SQL based
> > >>>solutions), NULL is a value and can be modeled mathematically with the
> > >>>empty set. In that case, a relation tuple with a NULL is as valid
> > >>>mathematically as one without. Agreed? --dawn
>
> > >>Well, if it's merely a matter of definition, then, "No. Not agreed."
>
> > > Since Dawn defines NULL as the empty set your answer implies that you
> > > think the empty set is not a value. Why?
>
> > > -- Jan Hidders
>
> > Partly (i) NULL is already overusedI am using it only one of the ways it is used, unless I qualify it as
> "SQL NULL" which is quite different from most other uses of NULL within
> the s/w development profession.
>
> > and (ii) the language
> > used on this thread is imprecise.All language is imprecise. We always make assumptions about what the
> other person be able to intrepret as it is intended. When there are
> differences of opinion, then it is helpful to increase precision in the
> definitions.
>
> > For instance, the reference to "relation tuple" in the
> > above paragraph: is she distinguishing between tuples
> > in relations and tuples otherwise? I was responding to JOG's statement
> > "A relation tuple with a NULL in it is no relation tuple at all. From a mathematical perspective,
> > case closed. "So I used the same language.
>
> > What, exactly, does
> > "valid mathematically" have to do with her point?
>
> [I realize I'm arguing against a point not explicitly made.] I was responding to JOG:
> > "A relation tuple with a NULL in it is no relation tuple at all. From a mathematical
> > perspective, case closed. "
> indicating that the this depends on the def of NULL. The case is
> closed from a mathematical perspective on an SQL NULL (which, I think,
> was JOG's point), but because he did not qualify or define the NULL, I
> wanted to be clear that the case is not closed on the use of NULL with
> databases, in general. That depends on the def of NULL.

Yes, an SQL null of course. Thanks for the clarification - although I'm not sure it was strictly necessary, and that /perhaps/ it's generated a wee bit of unnecessary noise in this thread. Received on Tue Oct 10 2006 - 01:20:12 CEST