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

From: mountain man <hobbit_at_southern_seaweed.com.op>
Date: Sat, 21 Feb 2004 23:28:09 GMT
Message-ID: <dQRZb.70077$Wa.44456@news-server.bigpond.net.au>

"Dawn M. Wolthuis" <dwolt_at_tincat-group.com> wrote in message news:c12ia2$p0l$1_at_news.netins.net...
> "mountain man" <hobbit_at_southern_seaweed.com.op> wrote in message
> news:r3%Yb.66336$Wa.13812_at_news-server.bigpond.net.au...
> > "Neo" <neo55592_at_hotmail.com> wrote in message
> > news:4b45d3ad.0402181740.42d42bc2_at_posting.google.com...
> > > Execute("SELECT * FROM BOB WHERE OUTPUT = FALSE");
> > >
> > > 19 Records Found:
> > > "Codd provided appropriate mathematical backing to all of his claims"
> >
> > ...[trim]...
> >
> > I'd be interested to hear about this. Empirical
> > evidence should either exist or not exist. The
> > "all" word might be troublesome.

>
> I have found at least one area where Codd takes a jump mathematically.
I'm
> not taking the time right now to get his exact wording, but a summary is
> this:

>

> 1. In his 1970 paper, Codd goes through the mathematics of relations and
> indicates that elements in relations could, themselves, be relations.
> However, he suggests starting simply with relations that do not contain
> relations.
> 2. In the 1974 paper and in the normal form discussions, normal forms are
> described so that "n" normal form is data that is in 1st normal form and
> then ...
> 3. There is no mathematical foundation for putting the data into 1NF
except
> for what Codd and his followers indicate is that the model should be as
> simple as possible but not simpler and they indicate that without
resorting
> to nested relations, the model is as simple as is needed. This is NOT a
> mathematical conclusion.

It seems to be more of an hypothesis.

> Even if we were to accept the non-mathematical
> statement that a model should be as simple as possible but no simpler,
there
> is no proof that for the user of a data model, it is simpler to have flat
> relations.

Flat relations meaning a direct mapping to "the real world"?

>I would suggest that there are tradeoffs and it is not at all
> clear that flat relations are a "simple" way to think about data.

Most database systems are evolving concerns, and the larger percentage of such on our planet today are managed using a symbiosis of relational mechanisms ruled by pragmatism.

Results are what count the most.

Pete Brown
Falls Creek
NSW
Oz Received on Sat Feb 21 2004 - 17:28:09 CST