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

From: Dawn M. Wolthuis <dwolt_at_tincat-group.com>
Date: Sun, 13 Jun 2004 13:12:16 -0500
Message-ID: <cai5e5$hrp$1@news.netins.net>


"mAsterdam" <mAsterdam_at_vrijdag.org> wrote in message news:40cc7f2b$0$34762$e4fe514c_at_news.xs4all.nl...
> Dawn M. Wolthuis wrote:
> "x" wrote:
> >>>So if I put my data into an MV database I can access it as if it were
in
> >>>an RDBMS. However, the converse is not true.
> >>
> >>So all data in a MV database can be represented in relational model,
> >>but not all data in a RDBMS can be represented in MV model :-)
> >>
> >>Which one is more expressive ? :-)
> >
> > Easy question --
> >
> > if each model can provide a solution for a particular area so that we
have
> > both an MV and a SQL-DBMS solution and
> >
> > if we can look at the MV model as relational when we choose to do so
(which
> > is usually for the purpose of using SQL against it)
> >
> > but we cannot take the relational model and view the MV model from it
> >
> > Then clearly the more expressive language is ... NOT the one that loses
the
> > ability to view the data in some other way, right? --dawn
>
> So now we have language R and language M.

A business problem is brought to people who encode a solution in R and in M. They make the usual design tradeoffs based on whichever implementation they are doing. The M solution can toggle to show you an R view of the solution, but the R solution does not have the ability to show an alternate M view of the solution. Now, you could design an R solution that does permit you to view it as this M solution, but you would have to have decided in advance to do that, otherwise it is likely you will make design decisions that rule out getting back to the original M solution.

> R 'loses the ability to view the data' from within M and that
> would somehow mean M is *more* expressive?
> The only way I could make sense out of that is
> if the (appearant) excess expressions in R could
> *not* be relevant to a solution.

>
> Do you have an indication as to what those excess expressions are?

they tend to be data that were collected and stored in the M solution and designed out (deemed unimportant to retain) for the R solution.

> Which statements can you make in R but not in M - IOW
> of which data does R lose 'the abitlity to view the data in some other
way'?

It is not what cannot be done, but what will not be done with R that is the problem.

> x's question may be easy, your answer sure isn't.

Sorry 'bout that. --dawn Received on Sun Jun 13 2004 - 13:12:16 CDT

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