Re: Database-valued attributes?

"Marshall Spight" <mspight_at_dnai.com> wrote in message news:fX7sb.174252$e01.608500_at_attbi_s02...
> "Paul Vernon" <paul.vernon_at_ukk.ibmm.comm> wrote in message
news:boqjj0$18lk$1_at_gazette.almaden.ibm.com...
> >
> > Just need to agree on what a database value actually is. If it is a
'set of
> > relations' what happens if two relations contain the same set of tuples
(of
> > the same type), but have different 'relation names'? Are they different
> > relations?
>
> Well, if you have two "top level" relvars in a database with exactly
> the same contents but different names, is that any problem? I'm not
> aware of any problems.

Principle of Orthogonal Design. But lets not go there.

> I would say "yes, they are different relations."

You mean "different relvars containing the same relation values"

> Consider: we create a relation var "Primes" for interesting prime numbers
> we've calculated, and a relvar "Perfect" for interesting perfect numbers
> we have calculated. We're just about to run the applications that will be
> filling these relvars, so they're both currently empty. So they have
> the same set of tuples of the same type, but are different relvars.

What is to consider?
I'd just use two tuple types. E.g.

    { <Prime:Integer> }
and

    { <Perfect_Prime:Integer> }

> > If so does that mean that if *relation variables* have names,
> > then *relation values* must also have names? I.e. I suggest that either
> > neither relation values and relation variables have names, or that both
do.
> > I suggest we cannot have either-or.
> >
> > :-)
>
> I guess I'm not following you. Maybe the smiley means you're being
> funny? But I don't get the humour.

No, my smiley was because I could say *a lot* more than I did above.

> Perhaps I'm just in overly-literal mode today.

Never a bad mode to be in. Perhaps you could ponder on this one. If a database contains relation *variables* does that mean that a Database Valued Atrribute also contains variables?

Regards
Paul Vernon
Business Intelligence, IBM Global Services Received on Tue Nov 11 2003 - 19:50:39 CET