Re: So let me get this right: (Was: NFNF vs 1NF ...)

"Jan Hidders" <jan.hidders_at_REMOVETHIS.pandora.be> wrote in message news:RurPd.10057$xU6.448623_at_phobos.telenet-ops.be...
> David Cressey wrote:
> >
> > 3. The elimination process referenced above and outlined later in the
paper
> > proves that this elimination doe not reduce the expressive power of the
> > reulting normalized collection of relations.
>
> Strictly speaking that is not exactly true. There is theoretical work
> that shows that sometimes you cannot flatten relations without losing
> information unless you cheat by introducing new domain values for
> encoding the removed sets.
>
> -- Jan Hidders

Jan,

Thanks. Please shed some more light on this.

By "this elimination" I was referring not to all flattening of relations, but only to the transformations outlined by Codd in the 1970 paper.

By "normalization" I meant only what the 1970 paper meant by normalization. Later works by Codd and others would have referred to this as "putting in first normal form", or something like that.

So.

Am I misreading something in the 1970 paper (as far as you can tell)? Did the 1970 paper assert something that later work proves to be untrue (mathematically)?
Does the theoretical work you refer to require tranformations not illustrated in the 1970s paper?
Is it somethnig else? Received on Sun Feb 13 2005 - 13:28:55 CET