Re: teaching relational basics to people, questions

On Nov 18, 1:08 am, com..._at_hotmail.com wrote:

> Go read a definition carefully. Eg wiki dknf.
> It's in DK/NF iff all constraints follow from the domain and key ones.
> So it's not in DK/NF iff some constraint doesn't follow from the
> domain and key ones,
> In other words, if there other constraints is just isn't *in* DK/NF.

But that's just my point: we *assumed* DK/NF, so there cannot be any other constraints. 6NF should logically be subsumed, if not else then vacuously.

> (It's not a very useful concept.)

Personally I find it very useful, at least as a mental aid, because it forces one to concentrate on the possibility of constraining your schema just a little bit further. No matter the means.

--
Sampo