Re: Codd provided appropriate mathematics ... (was Re: Relational and MV (response to "foundations of relational theory"))

But 1NF has been recently redefined by Date and others. So, what precisely is the definition of 1NF that is required for a relational database implementation, from your perspective? --dawn

"Bob Badour" <bbadour_at_golden.net> wrote in message news:79ednTWAxfBHLKLdRVn_iw_at_golden.net...
> If they are not 1NF, they are not relational. They may be the deformed
> step-children of the relational model, but they are not relational.
>
> "Eric Kaun" <ekaun_at_yahoo.com> wrote in message
> news:L9O%b.18045$HM4.16491_at_newssvr31.news.prodigy.com...
> Do you mean relational as in mathematics? The relational model for data is
a
> specific application of mathematical relations. Are those examples you
give
> below really relational in the sense of the relational data model? I doubt
> it. They might have something to do with mathematic relations, but that's
a
> different thing entirely.
> "Tom Hester" <$$tom_at_metadata.com> wrote in message
> news:bac94$403f841e$45033832$27879_at_msgid.meganewsservers.com...
> This is just plain false. There have been many relational models
proposed
> that are not 1NF. See for example, ABITEBOUL, S.; BIDOIT, N. Non first
> normal form relations to represent hierarchically organized data. In:
PODS,
> 1984. Proceedings. . .Note the date: 1984. This is supposed to be a
> database theory board but it seems more religious than theoretical!
>
> "Alfredo Novoa" <alfredo_at_ncs.es> wrote in message
> news:403f7915.12870647_at_news.wanadoo.es...
> > On Fri, 27 Feb 2004 08:01:43 -0600, "Dawn M. Wolthuis"
> > <dwolt_at_tincat-group.com> wrote:
> >
> > >> The Relational Model permits relation typed attributes, so
> > >> "multivalued" does not have any advantage. Collection typed
> attributes
> > >> don't violate 1NF.
> > >
> > >Yes, so the theory in RDM is evolving to the point where it might
> become
> > >more practical in its application.
> >
> > The understanding of The Relational Model is better now than in the
> > 70's, but the model is always the same.
> >
> > But relation typed values in base relations seem to have little
> > utility. The only good practical use I have found to the moment is to
> > use them to implement a candidate keys relation variable of a catalog.
> >
> > > But while each RDBMS vendor seems to
> > >have a means now of storing an array (or relation or other
> collections),
> > >querying against this data is done differently by each vendor, it
> seems,
> > >although SQL-99 has a means of doing this (and perhaps more db
vendors
> are
> > >employing that standard, but when I checked in 2002 there was no
> > >consistency).
> >
> > As you heared hundreds of times, SQL is not relational. You will not
> > find the term relational in the SQL specifications.
> >
> > >> Relations are in 1NF by definition. With a RDBMS you can not
violate
> > >> 1NF even if you want.
> > >
> > >You can violate any of the other normal forms, but not 1NF.
> >
> > Because you have no way. Relations are in 1NF by definition, otherwise
> > they are not relations. If a DBMS does not use relations then it is
> > not a RDBMS, so if you can violate 1NF then you are not using a RDBMS.
> > A simple tautology.
> >
> >
> > Regards
> > Alfredo
>
>
Received on Fri Feb 27 2004 - 22:21:56 CET