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:1002806784.345774_at_kang.qonos...
>
> "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.

It is not asserting anything about a location or an OID either; however, the unqualified string (or symbol) "Socrates" suffices to identify the individual to the participants of this discussion. Do you have a point?

> 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.

Agreed. The relational model allows this. Again, do you have a point?

> > As I said before, values are identity.
>
> Then why has sql:1999 introduced oids?

Because the majority of practitioners are ignorant of basics including many of those who participate on standards committees. Further, vendors who predominate on standards committees are eager to move work off their plates and onto the plates of their customers (as long as their customers do not perceive the detriment and as long as their competitors are eager to do the same). Received on Sat Oct 13 2001 - 17:42:56 CEST