Re: Pizza Example

"Jan Hidders" <jan.hidders_at_REMOVETHIS.pandora.be> wrote in message news:gdYec.70591$su1.4775030_at_phobos.telenet-ops.be...
> Eric Kaun wrote:
> >
> > [...] By nesting values inside values (and then
> > a further layer inside that, I believe), you complicate the algebras,
> > closure, and optimizations. Relational is much simpler, hence its power.
>
> That's funny.

I'm not laughing. :-)

> I somehow remember Date and Darwen proposing a relational
> model where you could have tuples containing sets that contained tuples
> .. et cetera. The horror! The heresy!! In fact, the whole 1NF thing
> seemed to have gone up in smoke, somehow. It still gives me the creeps
> when I think about it, every now and then ... Surely, that must have
> been a bad dream, right?

OK, I expressed myself badly. Logically, the relational user sees values in relations. The types of those values can be anything, including lists and such, but there shouldn't be operators in the data model to manipulate those - rather, those are user-defined operators for the specified types. Pick-like MV exposes the nesting as part of its logical model (at least I think, since it's not formally defined).

Is that better? Date's paper "What First Normal Form Really Means" talks about this in great detail...

• erk