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

"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. 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. 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.

--dawn Received on Thu Feb 19 2004 - 08:47:11 CST