Re: The Fact of relational algebra (was Re: Clean Object Class Design -- What is it?)
Date: Wed, 03 Oct 2001 22:44:14 -0300
Message-ID: <3BBBBEEE.30906_at_mac.com>
Daniel Poon wrote:
> "Leandro Guimarães Faria Corsetti Dutra" <leandrod_at_mac.com> wrote in message
>
>>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
Can you expand on that?
> definition of anymore). 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???
They didn't. It's not a redefinition, it's a definition. It's a branch of Mathmatics not because some pure Mathematician said so, but because Codd used Mathmatics to create it, and it is a logical theory using the tools, language and methods of Mathmatics -- but not in the realm of pure traditional Mathmatics.
Now, what other people have done is to bastardize the relational theory, but that's no Codd's fault -- and the tragical result is SQL.
What "fundamental concepts" do you think that relational algebra redefines?
>>>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. I think it would be a lot closer to
> set theory then. Set theory is what people use to 'implement' mathematics
> these days ;-)
Important as it may be, I do not know enough to understand your
question.
-- _ / \ Leandro Guimarães Faria Corsetti Dutra +55 (11) 246 96 07 \ / http://homepage.mac.com./leandrod/ BRASIL +55 (43) 322 89 71 X http://tutoriald.sourceforge.net./ mailto:lgcdutra_at_terra.com.br / \ Campanha fita ASCII, contra correio HTML mailto:leandrod_at_mac.comReceived on Thu Oct 04 2001 - 03:44:14 CEST