Re: Character string relation and functional dependencies

On Dec 8, 8:05 pm, "V.J. Kumar" <vjkm..._at_gmail.com> wrote:
> Tegiri Nenashi <TegiriNena..._at_gmail.com> wrote innews:cd2ad8bd-78ca-433d-bc0f-3e7ef0c0fe2a@e6g2000prf.googlegroups.com:
>
> > On Dec 6, 2:38 pm, Jonathan Leffler <jleff..._at_earthlink.net> wrote:
> >> Tegiri Nenashi wrote:
> >> > On Dec 6, 9:40 am, rp..._at_pcwin518.campus.tue.nl (rpost) wrote:
> >> >> Another difference is that database tables are finite and
> >> >> variable,
>
> >> > Oh, relations in database world are certainly not restricted by
> >> > finite cardinality.
>
> >> I thought that computers are finite, so the relations containable in
> >> them are too - even if damn large. There's a big difference between
> >> very large and infinite.
>
> > This doesn't really matter. You can still reason about infinite
> > relations
>
> You can do that with your brain...
>
> with finite resources available on you computer platform.
>
> but not with that. The computer is an intrinsically finite gadget.
> Therefore, you'd better use the finite model apparatus to reason about
> things like the impossibility of expessing transitive closure in the
> relational algebra. A lot of stuff like the compactness theorem does
> not work with finite models which makes infinite model proofs
> inapplicable in the finite case.
>
>
>
> >> One ultimate limitation is the uniqueness requirement. Suppose you
> >> have a table with two integer columns. Since the range of the
> >> integer types are finite (even if your DBMS handles multi-precision
> >> integers), then the maximum number of distinct rows in the relation
> >> is also finite.
>
> > All computer algebra systems work with numbers which are not
> > restricted by a whim of hardware architects. 16/32/64 bit integer
> > numbers (let alone floats)? give me a break!
>
> Jonathan is of course right, the set of 'floats' is clearly finite that
> somewhat clumsily approximates real numbers !

You fail.

Marshall Received on Sun Dec 09 2007 - 05:38:53 CET