Re: Proposal: 6NF

JOG wrote:
> 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.

This is entirely a matter if definition. I have worked with "NULL values" and with an SQL NULL. The first is a value. The way it might be handled in a 2VL language that works with such values could be modeled with the empty set. If you are talking about the SQL NULL or if you define the relational model to include 3VL (which it seems many theorists do not), then a NULL is defined as a non-value.

So, your above statement is entirely about the definition of NULL, right?

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 Received on Fri Oct 06 2006 - 22:21:07 CEST