Re: In an RDBMS, what does "Data" mean?
Date: Mon, 7 Jun 2004 09:51:13 +0300
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"Paul" <paul_at_test.com> wrote in message
> x wrote:
> >>consider the statements:
> >>1) Pete is 29 years old.
> >>2) Everyone's age is under 60.
> >>In a relational database the first would be data and the second a
> >>constraint. In Prolog would they both be data?
> > Nothing would stop you to say John is 84 years old.
> > It just follows that John isn't "everyone".
> In a DBMS, the constraint *would* stop you saying John is 84, that's the
> whole point of it. I presume that in Prolog it works in a similar way (I
> know, dangerous to talk about things I don't really know!). Surely Prolog
> wouldn't let you store two mutually contradictory statements?
> > I'm not sure about this.
> > There must be exactly *ONE* real-world "interpretation" of the database.
> Why must there?
> consider the database with one tuple like this: (1,2)
> There could be many real-world interpretations of this database surely?
> It's not inconceivable that two people who've never met have identical
> databases with totally different interpretations.
> >> > I'm not sure a database is a finite set of axioms.
> >>Why not? A databases is just a finite set of tuples from which you
> >>derive other truths.
> > It is not. It is a one-to-one corespondence with a piece of the
> > "real-world".
> OK maybe I shouldn't have used the world "just". But why can't a
> database be both? From a proof-theoretic point of view it's what I said.
> From a model-theoretic point of view it's what you said. The two aren't
> mutally exclusive.
But there is an exact match ? :-)
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