Re: The Fact of relational algebra (was Re: Clean Object Class Design -- What is it?)

"Daniel Poon" <spam_at_spam.com> wrote in message news:1002130531.352254_at_kang.qonos...
>
> "Leandro Guimarães Faria Corsetti Dutra" <leandrod_at_mac.com> wrote in
message
> news:3BBB41B8.7090202_at_mac.com...
>
> > Perhaps you should ask the people at http://dbdebunk.com./ -- there you
> can
> > contact the actual gurus that work with relational algebra, namely Chris
J
> > Date, Hugh Darwen, Fabian Pascal, and McGoveran.
>
> Thanks, I'll have a look later.
>
> > That's because relational theory was defined by EF "Ted" Codd... and is
> > restricted to database systems.
>
> I seem to remember the rdbms guys redefined 'completeness', to something
> that has no bearing on mathematical compeletness (which I cant remember
the
> definition of anymore).

"Seem to", "I can't remember"... Would you like to argue against something you know and can remember? It might prove a little more useful.

By any chance, are you referring to the difference operator vs. set negation? One uses an explicit finite universe and the other uses an implicit potentially infinite universe.

> I mean, mechanical engineers use applied mathematics
> to underpin their theories, but they don't go an redefine fundamental
> concepts on a whim! So why do computer scientists do that???

I doubt that mechanical engineers have much use for infinite in their daily jobs when applying mathematics. Recalling from my own electrical engineering background, such singularities only proved useful in frequency filter design.

> > > When applying relational algebra to computing, is it a fair assumption
> to
> > > say that it is a value based system? Mathematics always seemed more
like
> an
> > > identity based system to me.
> >
> > This part is too hight for me!
>
> But I think its kind of important. I think you could re-implement
relational
> algebra with identity based semantics.

Values are identity, which obviates the need for re-implementation.

> I think it would be a lot closer to
> set theory then. Set theory is what people use to 'implement' mathematics
> these days ;-)

I think you will find that the attempt ran into limitations.

>
> Cheers
>
> Daniel
Received on Sat Oct 06 2001 - 20:05:21 CEST