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Re: In an RDBMS, what does "Data" mean?

From: Dawn M. Wolthuis <dwolt_at_tincat-group.com>
Date: Mon, 14 Jun 2004 15:43:58 -0500
Message-ID: <cal2mk$e5k$1@news.netins.net>


"Eric Kaun" <ekaun_at_yahoo.com> wrote in message news:pgkzc.25517$_g6.23406_at_newssvr31.news.prodigy.com...
> "Dawn M. Wolthuis" <dwolt_at_tincat-group.com> wrote in message
> news:cage91$kif$1_at_news.netins.net...
> > Keep in mind that unlike an RDBMS schema, the vocabulary for MV/PICK
> systems
> > is descriptive of the data and not constraining. The same data can be
> > described in many different ways. The association would really be a
type
> of
> > derived data.
>
> How is this useful? I've seen this in COBOL layouts, and was underwhelmed;
> it always seemed to cause more problems (and invite even others) than it
> appeared to solve. How is this more effective than a view, for example?

Logically that is what it is, I guess, but it can be nested.

Take all of the nouns you want to consider and look at their relationships. Month, Day, and Year are three such nouns and you might want another that is made up of exactly these three -- so you can derive Date as Month | Day | Year or derive month, for example, using a function as Month(Date). Now, if you are looking at a list of dates, you can do the same thing, performing functions to group or separate various data.

I'm not sure that answered your concern. I think being underwhelmed regarding derived data is appropriate in 2004. smiles. --dawn Received on Mon Jun 14 2004 - 15:43:58 CDT

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