Re: MV Keys

"Jon Heggland" <heggland_at_idi.ntnu.no> wrote in message news:MPG.1e77690686affa66989793_at_news.ntnu.no...
> In article <g_6Pf.43111$F_3.27902_at_newssvr29.news.prodigy.net>,
> brian_at_selzer-software.com says...
> > > Um... yes. There is only one blue; that it can be used in different
> > > context with different meanings doesn't change that, and doesn't cause
> > > any redundancy.
> > >
> >
> > I think it does. If widgits is defined as a domain and lists of widgits
is
> > defined as a domain, and the same list of widgits can be arrived at
through
> > the use of the combinatorial rules of the universe, then the explicit
domain
> > definition is redundant.

> Why? And what do you mean by "arriving at a list of widgits through the
> use of the combinatorial rules of the universe"?

A list can be "stored" or derived data. It is redundant if it is both.

> > If you define constraints on the widgit list
> > domain, but construct some widgit lists in a database without
referencing
> > that domain, then those constraints cannot be enforced for every list of
> > widgits.

> So what? If you want domain constraints, you have to create a domain---
> which is then distinct from other domains. I can create a domain of
> integers between 42 and 5286; that does not preclude using integers
> outside that range elsewhere in my database.

How do you tell if two domains are distinct ? I guess they are because they are two :-)

> > >> Once you discard First Normal Form, all bets are off.
> > >
> > > What bets? Are you saying a database not in 1NF is logically
> > > unsound/inconsistent? 1NF is orthogonal to the other usual NFs, except
> > > if you arbitrarily define the others to include 1NF.
> >
> > I can't be sure, and that's enough for me to avoid applying NFNF like
the
> > plague.

> What aspects of FOPL and set theory are affected?

About what set theory do you speak ? Received on Tue Mar 07 2006 - 12:27:24 CET