Re: foundations of relational theory?

"Marshall Spight" <mspight_at_dnai.com> wrote in message news:BBnmb.21869$Fm2.11581_at_attbi_s04...
> "Tony Gravagno" <g6q3x9lu53001_at_sneakemail.com.invalid> wrote in message
news:7phbpv8g1h7m9g4csckol25ukoebjftvsv_at_4ax.com...
> > In my mind the answer to your questions is that a developer shouldn't
> > need to plan for every possible question that could be asked of
> > his/her database.
>
> Agreed.

Hence the importance of logical independence.

> > If we create an application where it's function is
> > (now or perhaps in the future) to identify a parent based on the name
> > of one of her children, then the database should be constructed to
> > account for that eventuality.
>
> That doesn't sound so good to me. Having the schema be dependent
> on what applications we anticipate is a problem. Normalization
> makes it possible to have the schema be dependent solely on
> the relations among the data, and therefor be the correct schema
> for all possible applications. This gets you want you wanted
> in your first sentence: the developer doesn't need to plan for
> every possible query. He already knows he's done the right thing.

Hence the importance of closure and of a sound notation for expressing logical derivations.

> > In reality any good application
> > developer can predict the nature of most of the queries that will be
> > asked of the database within a specific business context.
>
> I'm sceptical of this claim.

I am more than sceptical of the claim. The claim is bunk. If it were not bunk, software maintenance would cost nothing and version 1.0 of every application would suffice for all time.

> > That
> > drasically limits the permutations, and allows the developer to create
> > only those structures necessary to support the application. When we
> > have needs to extend out of the box it's no problem to reformat data
> > into new tables, or simply create extended definitions that point to
> > existing data.
>
> Wouldn't you agree that it would be better to have a system
> whereby no changes to existing applications are necessary to
> accomodate new applications?

Tony lacks the intellectual capacity to understand what actually does or does not limit permutations. Using only one structure in a logical data model in all cases limits the structural permutations to one at the logical level. Using any more than one structure causes the permutations to grow factorially. Received on Sat Oct 25 2003 - 15:59:00 CEST