Re: cdt glossary [Graph] (was: what are keys and surrogates?)
Date: Sat, 12 Jan 2008 10:48:25 -0800 (PST)
On Jan 12, 8:14 am, David BL <davi..._at_iinet.net.au> wrote:
> On Jan 12, 2:24 pm, JOG <j..._at_cs.nott.ac.uk> wrote:
> > On Jan 12, 1:05 am, David BL <davi..._at_iinet.net.au> wrote:
> > > Really! I have seen a (mathematical) relation formally defined as a
> > > subset of a cartesian product (and not an ordered tuple) on many
> > > occasions.
> > Bit confused by this - a cartesian product generates a set of ordered
> > tuples (over which a function is a subset), and all the hyperlinks you
> > listed seemed to follow that description.
> Do you agree that most authors define a binary relation as a set of
> ordered pairs? In an earlier post you said a function is the ordered
> triple (D,C,G). How do you reconcile saying that a function is a
> (binary) relation?
Relations are formally described by the ordered triple (D,C,G), but are often informally described by just G. I don't really see any problem there - if it's vital to know D and C then they will be stated, and if they are not, well we can still formulate an approximation of them by looking at the elements of the couples in G anyhoo.
Now Multivalued Functions - there's worth something arguing about ;) Received on Sat Jan 12 2008 - 19:48:25 CET