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Re: database design method

From: Bob Badour <bbadour_at_golden.net>
Date: Mon, 11 Nov 2002 22:10:18 -0500
Message-ID: <nl_z9.303$pV4.163278957@radon.golden.net>


"Jan Hidders" <hidders_at_REMOVE.THIS.uia.ua.ac.be> wrote in message news:3dd011dd$1_at_news.uia.ac.be...
> D Guntermann wrote:
> >
> >Moreover, Mr. Date, in chapter 11, does go on to say that it seems
> >prefereable to avoid relation-valued attributes, at least for base
relation
> >variables in most cases, because they are asymmetric and provide a degree
> >of needless complexity.
>
> I fully agree with Date here. In fact, I would even go further then that.
> IMO we should stick with the original flat interpretation of the
relational
> model, (so not even relation-valued attributes) but with the addition that
> we allow domains of abstract identifiers (or object identifiers if you
want
> to call them that).

With user defined types, one can define whatever type one wants. If you want a type to use as an abstract identifier, just define one. Ordered, unordered whatever you want. Just tell the DBMS what operations it has.

> People often forget that the requirement that the domains
> should not contain abstract identifiers is something where the relational
> model deviates from first-order logic.

How so? The relational model allows full support of user defined types.

> But perhaps one of these days Date will explain to use that this is what
> Codd had meant all along. :-)

Perhaps, one day.

> -- Jan Hidders
Received on Mon Nov 11 2002 - 21:10:18 CST

Original text of this message

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