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Re: Normalization by Composing, not just Decomposing

From: Dawn M. Wolthuis <dwolt_at_tincat-group.com>
Date: Mon, 12 Apr 2004 14:59:40 -0500
Message-ID: <c5esfv$hi$1@news.netins.net>


"Alan" <alan_at_erols.com> wrote in message news:c5erh9$qt9b$1_at_ID-114862.news.uni-berlin.de...
> Normalization rules are Codd's rules, not God's rules. They are a _guide_
to
> distributing data among entities, not a dogmatic recipe. You seem to want
to
> project a certain amount of dogmatism on everything, as if life were black
> and white. It isn't, it's an infinite number of shades of gray (well
16,384
> at least).

Who, me? Perhaps it comes across that way bz I am new to doing any sort of significant study of database theory and compared to everything I have worked on before, relational theory IS very tightly pre/described with a mathematical model. The model is tight but that doesn't mean it is equally tightly implemented. I'll agree completely with the infinite number of shades of gray -- I'm guessing even uncountably infinite.

> Did you hear about the programmer they found dead in the shower? He was
> stiff, grasping a bottle of shampoo, his eyes apparently fixed on the
> instructions, "Lather, rinse repeat."
>
> Here's the general rule of thumb: Normalize to 3NF, and then see if that
> works for you in your situation. If it doesn't, then denormalize or
> normalize further. Iterate.

But I don't want to put the data in 1NF -- there is no reason to do so from my perspective. Since all other normal forms require the data to be in 1NF first, that pretty much kills the process as it is written. However, since I can put data into (2NF - 1NF) and (3NF - 1NF) that is what I do and then proceed as you describe to refactor the model until it fits.

> You ask, "Are you adhering to relational theory when deploying an OLAP
> database where
> the data is in fact & dimension tables?" Did you read my message? What did
I
> write about normalization and the star schema?

I'll re-read and see if it clearer, but it seems to me that you were making a pitch for OLAP data being "relational" in some way. Sorry if I misunderstood.

> Data is not _modeled_ as "OLAP cubes". Cubes are an implementation,
> modelling is analysis and maybe design.

Cubes could be an implementation, but they could also be used to model the data. There is not always a need to take the data, put it into a relational data model and reform it for OLAP -- one could go from requirements to OLAP data model, right? --dawn

>
> "Dawn M. Wolthuis" <dwolt_at_tincat-group.com> wrote in message
> news:c5ecb7$e2f$1_at_news.netins.net...
> > "Alan" <alan_at_erols.com> wrote in message
> > news:c5e6m0$lo87$1_at_ID-114862.news.uni-berlin.de...
> > > Realtional theory as a data theory is analagous to democracy as a form
> of
> > > government- it may not be perfect, but so far, there's nothing better
in
> > > most cases.
> >
> > Have you concluded this by reviewing some emperical data that has been
> > collected or because you adhere to some philosophy or what? Could I
state
> > something contradictory with as much logical backing?
> >
> > > Denormalization in itself has nothing directly to do with OLAP, except
> > that
> > > one may denormalize more for an OLAP application than an OLTP
> application.
> > > However, in OLAP, you are not necessarily denormalizing so much as
> > > "re-normalizing", in that you are really developing a diiferent
> > distribution
> > > among entities for the same data, such as in a star schema. It's not
> > > normalized, but it's not denormalized either. It's just different. I
> > suppose
> > > an argument could be made that (in the case of a star schema), you
start
> > > with a normalized schema, and then apply transformation rules (no,
don't
> > ask
> > > me what they are- there are books on the topic) to transform it into a
> > star
> > > schema. Think about it- a basic star schema is essentially a giant
> > > many-to-many linking table (the fact table) with a bunch of
descriptive
> > data
> > > tables (dimensions).
> >
> > Are you adhering to relational theory when deploying an OLAP database
> where
> > the data is in fact & dimension tables? I have not seen a star schema
for
> > the purposes of OLAP without some rules broken such as duplication of
> data.
> > But I'm fine with it either way -- just curious whether most relational
> > theorists would view data modeled as OLAP cubes as following "the
> > ules". --dawn
> > <snip>
> >
> >
>
>
Received on Mon Apr 12 2004 - 14:59:40 CDT

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