Re: Can we solve this -- NFNF and non-1NF at Loggerheads

From: Alan <alan_at_erols.com>
Date: Mon, 7 Feb 2005 13:06:50 -0500
Message-ID: <36pp1rF4u7s98U1@individual.net>

"Dawn M. Wolthuis" <dwolt_at_tincat-group.comREMOVE> wrote in message news:cu8967$iqj$1_at_news.netins.net...
> "Paul" <paul_at_test.com> wrote in message
> news:42079da8$0$34063$ed2e19e4_at_ptn-nntp-reader04.plus.net...
> > Alan wrote:
> >>> Roy Hann wrote:
> >>>
> >>>> 1NF does not "mean values are simple or indivisible". It just
> >>>> says that for the purpose of the relational theory, the
> >>>> divisibility (or internal structure) of values of a given type is
> >>>> of no interest or use within the theory. The theory does not
> >>>> make use nor reference to the internal structure of a value of
> >>>> any type. The theory therefore does not need to define what
> >>>> atomic means. The term "atomic" is a just a narrative short-hand
> >>>> that Codd used to say, "That's stuff I don't care about, so forget
> >>>> about it from now on as you read this paper." I can't
> >>>> think of any other theory where a precise definition is demanded
> >>>> for things that are *intended* not to be discussed. Plane
> >>>> geometry isn't required to define colour for the purpose of
> >>>> excluding it from discussion.
> >>>>
> >>>> There is nothing in RT that *prevents* values from being
> >>>> divisible, there never was, and it would plainly be stupid to
> >>>> want it that way.
> >>>
> >>> This sounds to me like an excellent summary of what "1NF" and
> >>> "atomic" means. I can't believe we go round in circles discussing
> >>> this point when it really is this simple!
> >>
> >> Okay, I will cite a well respected source supporting my position, then
> >> you
> >> do the same. From "Fundamentals of Database Systems, Third Edition",
> >> Elmasri/Navathe, pages 485-487 Addison-Wesley, 2000:
> >
> > I don't see a conflict between the extract below and what Roy said
above.
> > Just that the text below is a bit on the verbose and practical side, and
> > the above is a more abstract, concise and clear version.
> >
> > I don't think most of the people here actually disagree with the basics,
> > just that there is a problem with expressing the ideas in written
language
> > such that they aren't misinterpreted.

>

> I think it would be great to have 1NF in our currently-not-being-addressed
> glossary of terms (mAsterdam - any chance you could send the current
> version?) so that we can point to that for any future discussions. Given
> that XML does not require 1NF (by most definitions), this topic is not
going
> away any time soon and starting such discussions by first getting everyone
> on the same page with a definition just holds up progress.

>

> Can we find a definition that is clear; preferably concise; is not about
> history (i.e. is a good definition for today);

The Elmasri staement regarding "historically" is there to put the explanation in context. It does not mean that the explanation is history. The explanation is 100% valid today.

 and does not require any
> redefinition of mathematical terms for which there is considerable
agreement
> (such as relation)? I suspect that whatever we come up with would
> contradict Date & Darwin, so if we could additionally ensure that the
> definition is mainstream and what the industry accepts as 1NF, then
perhaps
> we need a new name for the new definitions put forth by them? Just a
> thought. --dawn

>


> > Paul.

> >

> >> "First normal form (1NF) is now considered to be part of the formal

> >> definition of a relation in the basic (flat) relational model (Footnote

> >> 11:

> >> This condition is removed in the nested relational model and in

> >> object-relational systems (ORDBMSs), both of which allow unnormalized

> >> relations.); historically, it was defined to disallow multivalued
> >> attributes, composite attributes, and their combinations. It states
that
> >> the
> >> domain of an attribute must include only atomic (simple, indivisible)
> >> values
> >> and that the value of any attribute in a tuple must be a single value
> >> from
> >> the domain of that attribute. Hence, 1NF disallows having a set of
> >> values, a
> >> tuple of values, or a combination of both as an attribute value for a
> >> single
> >> tuple. In other words, 1NF disallows "relations within relations" or
> >> "relations as attributes of tuples." The only attribute values
permitted
> >> by
> >> 1NF are single atomic (or indivisible) values. ...
> >> The first normal form also disallows multivalued attributes that are
> >> themselves composite. These are called nested relations because each
> >> tuple
> >> can have a relation within it..."
> >>
> >> Your _opinion_ is not solicited. Cite some facts from a published
source.
> >>

> Received on Mon Feb 07 2005 - 12:06:50 CST