Re: Distributed foreign keys (was Re: Category Types)
Date: Wed, 25 Jun 2003 11:41:52 -0700
Message-ID: <jmednUet9vVtcWSjXTWc-g_at_speakeasy.net>
"Paul Vernon" <paul.vernon_at_ukk.ibmm.comm> wrote in message
news:bdcm8b$cvm$1_at_gazette.almaden.ibm.com...
> "Bob Badour" <bbadour_at_golden.net> wrote in message
> news:TtkKa.509$LI6.68898946_at_mantis.golden.net...
> [snip]
> > > >What do you propose for logical independence if not views?
> > >
> > > Alternate, information equivalent, database schemas.
> >
> > And how does this differ from views?
>
> Because to the user of a particular database schema sees as a table, what
a
> user of an alternate schema would see as a view. Giving a user a view and
> telling him it's a table is not good enougth unless the catalog reflects
that
> fact (including showing that any tables that the view is based on are
actually
> views, and acuratly reporting the constaints on the table that used to be
a
> view).
Fully exposing all the underlying constraints seems to me to be implied and required by a proper definition of the concept of a view.
>
> In otherwords, the concept of views does not properly capture the 'schema
> switching' process that should (logically) occur when you want to treat a
set
> of views as tables
Perhaps because we haven't really been reasoning at the level of an entire schema per each application view of the enterprise database, and so don't have terminology or syntax to manage this as an aggregate. I'm reminded of the old codasyl 3-schema architecture whereby one defined sub-schemas for this purpose (well, in theory anyway).
-- David Best (Remove the obvious to reply)Received on Wed Jun 25 2003 - 20:41:52 CEST