Re: atomic

On Nov 7, 12:25 pm, paul c <toledobythe..._at_ooyah.ac> wrote:
> David BL wrote:
>
> ...
>
> >> I think of these as symmetrical REFERENCE'ing statements and they are
> >> implicit from the choice of attributes of a relation. For me, this
> >> means that the orthodox view is that the form of optional data must
> >> involve more than one relation. So if set-valued attributes are
> >> eligible in the orthodox framework, I think I'd want to be able to say
> >> similar sentences about them.
>
> > Are you saying you want to make statements about sets without those
> > statements being reinterpreted as instead applying to the elements of
> > the sets?
> > ...
>
> I'm not sure if I understand you but at first glance I'd say no, that's
> not what I "want". I think if there is missing information then we
> can't express that in a conventional RM theory without multiple
> relations.

I agree.

I'm assuming you are referring to the idea of going to 6NF to allow for missing information.

> Maybe I'm misunderstanding, but I think RM allows sets to
> make statements about something we're interested in whereas statements
> about those sets are something else.

I was thinking of when you were saying in another post that r1 |x| r2 is empty, I regard that as reasonable on the assumption that statements are being made about the sets, thought of as single values, rather than the elements of the sets, and this indeed is appropriate for D&D definitions.

I'm hoping that you'll see mv-relations as a distinct formalism which avoids the need for 6NF, but has its own disadvantages that may make it unpalatable. Received on Wed Nov 07 2007 - 04:56:45 CET