Re: Relational Databases and Their Guts
Date: Wed, 25 Jun 2003 10:45:46 -0400
Message-ID: <yrjKa.505$My6.68419676_at_mantis.golden.net>
"Paul Vernon" <paul.vernon_at_ukk.ibmm.comm> wrote in message
news:bdbs2l$1l6u$1_at_gazette.almaden.ibm.com...
> "Bob Badour" <bbadour_at_golden.net> wrote in message
> news:AH3Ka.442$0j4.62704888_at_mantis.golden.net...
> > "Paul Vernon" <paul.vernon_at_ukk.ibmm.comm> wrote in message
> > news:bd9ao7$13qa$1_at_gazette.almaden.ibm.com...
> [snip]
> > > > Now, what in your mind means logical data independence?
> > >
> > > Strictly I think of it as:
> > >
> > > The ability to interact with a database via any information
equivalent
> > > database schema.
> >
> > That ability is trivial. How does it provide independence? How does it
allow
> > one to change the base relations to a different information equivalent
> > schema without requiring one to alter existing applications? Your
statement
> > above only requires that one can change the application to use the new
> > schema, and I do not think that provides any independence at all. Or am
I
> > missing something?
>
> Let me reword it as:
>> multiple information equivalent[subset] database schemas defined to the
> The ability to interact with a [subset of a] database via any one of
RDBMS
> >
> "base relations" are in the eye of the beholder.
>
> Logically, all equivalent schemas are equal, there is no requirement to
make
> one more equal than the others by making it 'primary'. Other than each
user
> choosing one as their current schema that is.
>
> Physically, one schema will be picked as the basis for physical
> implementation. This schema can be called "base" if you wish, but users
should
> not care.
I still do not see how one will specify the information equivalent schemas without views. With updatable views, users should not care either.
What is different from views in what you are suggesting? Received on Wed Jun 25 2003 - 16:45:46 CEST