Re: Can we solve this -- NFNF and non-1NF at Loggerheads

"Dan" <guntermann_at_verizon.net> wrote in message news:1107803519.389485.310840_at_z14g2000cwz.googlegroups.com...
> "BECAUSE of Date & Darwin's (relatively) new definition of 1NF. Can
> you not see from Date's new definitions that now a relation can be in
> 1NF even if there is a list, queue, stack, set, relation, linked list,
> hash table, or ... as the value of an attribute in that relation? Date
> adds somewhere
> (maybe that is in the "legal value" def?) that the only such data
> structures he would accept would be relations, but even if his
> definition of 1NF only permits that construct, it changes the meaning
> of 1NF significantly, right? How many practitioners today would say
> that they are putting a relation in
> 1NF and then proceed to leave nested relations in the model? That
> muddies the water a lot from my perspective, with the work I am doing.
> Make sense? --dawn "
>
> I think this new 1NF also totally invalidates a general principle of
> orthoganality of type to the relational model. Has Date explicitly
> stated that this principle no longer holds true somewhere?

I should re-read his papers on 1NF to see if I can tap into his thinking on this again, but I think his take is that this definition does uphold that principle. I cannot find a good quotation for that quickly, however.

From p. 152 of the same book:

"The main reason we mention the possibility of relation-valued attributes here is that, historically, such a possibility has usually been regarded as illegal. Indeed, it was so regarded in earlier editions of this book.... here is a ... excerpt from the sixth edition ... later in the same book, we find 'Domains (i.e. types) contain atomic values only ...[Therefore,] relations do not contain repeating groups...These remarks are not correct, however...They arose from a misunderstanding on this writer's part of the true nature of types (domains)."

It seems his restricting these collection types to relations is separate from his definition of normalization, but you are right that if he does restrict these types to relations (and I thought I read that somewhere), then that would change the relationship between types and the relational model. Hmmmm. The definitions of normalization allow for any type to be defined, so perhaps he deems it to be a "best practice" instead of a requirement for relations that any nested "data structures" be relations? I cannot recall and I'm not feeling like digging any deeper right now. Anyone? --dawn

> Thanks,
>
> Dan
>
Received on Mon Feb 07 2005 - 20:31:26 CET