Re: atomic

On Nov 1, 8:07 am, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
> paul c wrote:
> > Bob Badour wrote:
>
> >> paul c wrote:
>
> >>> David BL wrote:
>
> >>>> On Oct 31, 4:31 pm, "Roy Hann" <specia..._at_processed.almost.meat>
>
> >>> ...
>
> >>>>> 1NF does not *require* that values be atomic. It asserts that
> >>>>> values will
> >>>>> be *treated as* atomic. Big difference. Essential difference.
>
> >>>>> Roy
>
> >>>> Can that be formalised? I agree with Bob that in general we have a
> >>>> set of operators and they can allow us to see internal structure.
> >>>> What does it mean for a value to be *treated* as atomic?
>
> >>> I think it means that relational algebra operators are not allowed to
> >>> decompose it.
>
> >> Actually, the structure is illusory and representation-dependent.
> >> Domains have operations that appear to reveal internal structure even
> >> when that internal structure may not physically exist.
>
> > Okay, maybe it's clearer to say that relational algebra operators don't
> > decompose (attribute) values.
>
> I did not mean to imply I disagreed with you. I don't see David's posts
> directly, and I responded to what he wrote because you excerpted it.
>
> It's true the relational operations do not decompose attribute values.
> There are a number of contexts where one can apply operations to values
> including operations that seem to expose some structure.
>
> My point was even when operations seem to expose some structure, the
> structure does not need to physically exist anywhere. If we are "seeing
> internal structure" as David says, that structure may be a figment of
> our imagination.

Agreed, if you assume structure means physical structure.

>
> He seemed to suggest we need to have some formal way to see physical
> structure. I disagree with that wholeheartedly.

No, I was only suggesting that Roy couldn't formalise what atomic means. Received on Thu Nov 01 2007 - 06:40:28 CET