# Re: what are keys and surrogates?

Date: Mon, 14 Jan 2008 13:11:35 -0800 (PST)

Message-ID: <09cb8bd7-1896-43a8-a91d-af88906e6d73_at_e23g2000prf.googlegroups.com>

On Jan 14, 2:51 pm, "David Cressey" <cresse..._at_verizon.net> wrote:

> "vldm10" <vld..._at_yahoo.com> wrote in message

*>
**> news:8c40c81a-2278-4727-b3ae-158cdc87e8e2_at_q77g2000hsh.googlegroups.com...> On Jan 13, 4:41 pm, "David Cressey" <cresse..._at_verizon.net> wrote:
**> > > "David BL" <davi..._at_iinet.net.au> wrote in message
**>
**> news:b05f3396-4c1f-4710-8d27-d4940b7e689f_at_e10g2000prf.googlegroups.com...
**>
**>
**>
**> > > > This however doesn't change the fact that most authors define a
**> > > > (mathematical) relation as a set of ordered tuples, which means a
**> > > > function is not a relation (assuming, as most do, that a function has
**> > > > a defined domain and codomain).
**>
**> > > I don't understand how the conclusion follow from the premise.
**>
**> > I am afraid that you don't understand above conclusion because you
**> > don't understand what function is.
**>
**> What makes you think that?
*

Definition1 A function from A to B is a rule that assigns, to each member of set A, exactly one member of set B.

Is this good or bad definition for a function?
If you thing that this is good definition for a function then please
explain why this is good definition, else please explain why it is not
good definition.

Your answer on my question will be also answer on your question.
Received on Mon Jan 14 2008 - 22:11:35 CET