Re: Proposal: 6NF

Brian Selzer wrote:
>
> I agree. If the physical models are identical, then the performance would
> be similar. But common sense argues against the idea that the physical
> models should be identical. If {i, a, b} and {i, a}, {i, b} are equivalent,
> then since i, a and b are of the same types, it would take at least 1/3
> extra storage in separate tables because each i would occur twice.
>

That is pure speculation. When I said identical I meant precisely that. The only difference is in the metadata. There is no reason at all to store any values of i twice. Why should there be? If it is the same key value of the same type then it seems perfectly sensible to store it only once regardless of how many relations it appears in.

If you want to speculate some more then consider that only two bits of metadata may need to be added per tuple, which is presumably exactly the same as would be used to support nullable columns.

> I agree that decomposition into separate relations still has its place. I
> just don't think that nulls should be dismissed arbitrarily.

I have not dismissed nulls arbitrarily. There are good reasons to reject SQL's definition of a null. I'm still waiting for your definition. Apparently you don't have one for numerics so dare I ask if you have one for boolean? Do you have a null for a graphics image type or a date type or a cartesian co-ordinate? How does your null behave under the operators for those types? I think you have your work cut out here...

-- 
David Portas