Re: Define "flatten database" ?

From: Alan <not.me_at_rcn.com>
Date: Sun, 30 Jan 2005 21:28:55 -0500
Message-ID: <365jjsF4nn7hlU1@individual.net>

"Dawn M. Wolthuis" <dwolt_at_tincat-group.comREMOVE> wrote in message news:ctjk9u$h1u$1_at_news.netins.net...
> "Jan Hidders" <jan.hidders_at_REMOVETHIS.pandora.be> wrote in message
> news:WPWKd.8976$tX7.741404_at_phobos.telenet-ops.be...
> > Dawn M. Wolthuis wrote:
> >> "Alan" <alan_at_erols.com> wrote in message
> >> news:35vdofF4rvh8nU1_at_individual.net...
> >>>"Dawn M. Wolthuis" <dwolt_at_tincat-group.comREMOVE> wrote in message
> >>>news:ctdn9o$7sq$1_at_news.netins.net...
> >>>>"DA Morgan" <damorgan_at_x.washington.edu> wrote in message
> >>>>news:1106859773.807419_at_yasure...
> >>>>>silversw2000_at_yahoo.com wrote:
> >>>>>>
> >>>>>>Can someone define "flatten database" for me, in 100 words or less
(OK
> >>>>>>500 words is fine).
> >>>>>
> >>>>>Denormalize.
> >>>>
> >>>>I would guess "normalize" is more likely. [...]
> >>>
> >>>Flattening is DEnormalizing. Period.
> >>
> >> OK, I'd vote for both terms being incorrect. It is not denormalizing
> >> because it is starting with non-1NF data -- agreed? And it is not
> >> normalizing because, well, it clearly isn't (the key, the whole keyu
and
> >> nothing but the key ...).
> >
> > Can I try to bring some light here?

>

> Yes, you are always welcome!

>


> > Some database texts actually do treat the step from NFNF (or UNF or

> > non-1NF or whatever you want to call it) to 1NF as the first step of the

> > normalization process which makes it valid to call this step

> > "normalization". Note that normalization means in general that you are
> > transforming something such that it afterwards adheres to a certain
normal
> > form, i.e., a form in which it satisfies certain criteria, and that is
of
> > course exactly what is happening in this step. So the term
"normalization"
> > is certainly justified and correct.
> >
> > However, it is also defendable to classify it as denormalization since
one
> > of the goals of normalization was to remove redundancy, but flattening
the
> > database may actually introduce redundancy, which sets it somewhat apart
> > from the other steps. Since in industry the term normalization is often
> > loosely used synonymously with any form of restructuring of the schema
> > that removes redundancy, it then makes sense to see it as
denormalization.
> > But, from an academic point of view that is not strictly correct.
> > Obviously, *defining* flattening as denormalization is clearly wrong,
even
> > under the latter interpretation, since not all denormalization is
> > flattening.

>
> Yes -- thanks, you clearly were tracking with me and it looks like Alan
now
> understands this point too. He wants to say that when you flatten you
> ALWAYS are denormalizing, which seems to me to have a semantic problem,
but
> otherwise I understand that point. If you start with data that are not
> normalized, do we say we are denormalizing if we introduce more
redundancy?
> Or should we reserve the term "denormalize" for times when we start with
> data that are at least in 1NF and head to a structure that is not? I'm OK
> either way, but it makes a difference in whether I can give a counter
> example to Alan's claim or simply agree with it.

Let's reserve "denormalizing" for occasions when we start with data that is at least 1NF. Otherwise, we are "reorganizing". Actually, what say we not use "flatten" at all? We are either normalizing (always moving up the normalization steps), denormalizing (always moving down the steps), or renormalizing (either a sideways move in normalization or correcting an error that does not make substantial changes), or reorganizing (working with NNF data, but not normalizing it). Received on Sun Jan 30 2005 - 20:28:55 CST