Re: what are keys and surrogates?

"David BL" <davidbl_at_iinet.net.au> wrote in message news:1d8bc808-c202-45bd-8d04-5ad80bb895ef_at_n22g2000prh.googlegroups.com...
> On Jan 10, 5:05 pm, "David Cressey" <cresse..._at_verizon.net> wrote:
> > "David BL" <davi..._at_iinet.net.au> wrote in message
> >
> >
news:e6ba98c3-bc53-45a6-87c6-ea11e8c88616_at_p69g2000hsa.googlegroups.com...
> >
> >
> >
> >
> >
> > > On Jan 10, 1:22 am, Marshall <marshall.spi..._at_gmail.com> wrote:
> > > > On Jan 9, 8:07 am, David BL <davi..._at_iinet.net.au> wrote:
> >
> > > > > On Jan 9, 1:25 pm, Marshall <marshall.spi..._at_gmail.com> wrote:
> >
> > > > > > This issue goes away if we relax 1NF and allow attributes that
are
> > > > > > lists or relations. This gives us nested structures. (Nested
> > relations
> > > > > > are not particularly controversial around here.)
> >
> > > > > In addition to my previous post, I wish to add another comment
> > > > > regarding my suspicion with RVAs. The tuples of a relation are
> > > > > supposed to represent facts, but what does it mean when a relation
> > > > > merely represents a value?
> >
> > > > The question is meaningless. The distinction you are drawing
> > > > does not exist.
> >
> > > In what sense do tuples of an RVA represent propositions in *the* UoD?
> >
> > > > > Isn't the RM meant to have some close
> > > > > association with FOPL?
> >
> > > > Yes.
> >
> > > > > It seems to me there is a fundamental difference between
> >
> > > > > a) a large collection of propositions relevant to a particular
UoD;
> > > > > and
> >
> > > > > b) a composite data structure such as an AST which simply
> > > > > "is what it is"
> >
> > > > This is an illusion. There is no difference.
> >
> > > Hmmm. Unfortunately you didn't respond to my last paragraph which was
> > > more tangible.
> >
> > > I don't believe the distinction is an illusion. I'll have a go at
> > > providing an objective measure on a given relational database d...
> >
> > > Let B(d) equal some measure of the amount of information in d,
> > > quantified as the total number of bits required to store all the data
> > > (accounting for "compressibility").
> >
> > Off topic.
> >
> > I prefer quantified as the difference in entropy between the state that
> > includes d and the state that excludes it. I believe that, except for a
> > scale factor, the two measure boil down to the same thing, except for
one
> > subtle difference:
> >
> > Using entropy as the measure enables one to consider information content
as
> > being context sensitive. That is, if d is to be included in some other
> > database e, then the information provided by d to e is the entropy
> > difference between e and e+d (where "+" is suitably defined).

>

No. Did I say something that implies that? Received on Thu Jan 10 2008 - 20:28:10 CET