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

"Bob Badour" <bbadour_at_golden.net> wrote in message news:cd3b3cf.0110101647.4c4358cb_at_posting.google.com...
> "Daniel Poon" <spam_at_spam.com> wrote in message
news:<1002618908.638568_at_kang.qonos>...
> > "Bob Badour" <bbadour_at_golden.net> wrote in message
>>
> > > Values are identity, which obviates the need for re-implementation.
> >
> > Values are not identities. Vaules are only unique in their domain. For
> > example, each member of the 'Set of all employee keys', is unique only
in
> > that set.
> > E = set if employees
>
> E is a set of self-identifying values
>
>
> > D = set of departments
>
> D is another set of self-identifying values
>
>
> > Ek = set of employee keys
>
> Ek is a different set of self-identifying values
>
>
> > Dk = set of department keys
>
> Dk is yet another different set of self-identifying values

Look at this bit of logic "Socrates is a man"

i.e. Man(Socrates)

It is not asserting anything about a string of ascii characters or any other kind of key.
Socrates is also a member of the Universal set, and a lot of other sets. The fact that he belong to these sets is independant of his existance.

> As I said before, values are identity.

Then why has sql:1999 introduced oids?

Regards

Daniel Received on Thu Oct 11 2001 - 15:27:29 CEST