Re: Distributed foreign keys (was Re: Category Types)

"Paul Vernon" <paul.vernon_at_ukk.ibmm.comm> wrote in message news:bdv32u$14r6$1_at_gazette.almaden.ibm.com...
> "Lauri Pietarinen" <lauri.pietarinen_at_atbusiness.com> wrote in message
> news:3EF9EB5A.3060403_at_atbusiness.com...
> > So we really end up with
> >
> > 1) a bunch of datatypes (or domains)
> > 2) a set of relation variables (or schemas)
> > 3) a set of integrity constraints
> >
> > Did I leave anything out?
> >
> > It's pretty simple when you get down to the bottom of it!
>
> Absolutely and therein lies half it's beauty.
>
> Even better than the above however, is that if you consider relation
variables
> themselves simply as constraints on the possiable tuple types in the
database
> variable and that if you have no such constraints then any tuple types are
> allowed, and you also consider datatypes to be 'external' to the model
(and so
> are not needed to exist in the catalog) then the simplest database
possable is
> (I think) just the empty database.
>
> So all we have in minimum is
>
> D - the database variable
> d - the value of the D == {} - the empty set (of tuples)

Can a database value ever really be empty? What about the system catalog? Or is the system catalog a database value derived from a database value? I think the system catalog is part of the possible representation of a database value. Received on Wed Jul 02 2003 - 22:19:43 CEST