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Re: completion of action: 2001-07-27#2 (long)

From: pat hayes <phayes@ai.uwf.edu>
Date: Tue, 4 Sep 2001 12:40:01 -0700
Message-Id: <v04210105b7badb3e83fd@[130.107.66.237]>
To: Brian McBride <bwm@hplb.hpl.hp.com>
Cc: w3c-rdfcore-wg@w3.org
>pat hayes wrote:
>
> >
> > OK, but then this really does not make sense, because the M&S also
> > says that 'Resource' includes off-webbish things like (real) books.
> > So taken quite literally, this would allow a Statement to be a triple
> > whose second element is, say, volume 1 of the 1815 edition of
> > Brittanica. (Not an URI of said book, but the actual book itself,
> > with leather covers, weighs around 3 lbs.)
>
>I'm not going to argue mathematics with you Pat.  Long time passin',
>when I was first taught about sets, I was taught that a set could
>contain physical objects, i.e. the set of books on my bookshelf is a
>legitimate set.  Was that wrong?

No, that's the usual idea. (There are those who would disagree, but 
I'm not one of them.)

>Similarly, in the mathematical concept of a tuple, e.g. (x,y,z) can
>the components be physical objects, even though the tuple itself is
>an abstract thing?

Sure, an *arbitrary* mathematical triple. But if you go on to talk 
about these triples as constituting a *language* - one that can be 
parsed, has a grammar, and so on - then you are no longer understood 
to be talking about arbitrary triples, but those containing 
language-like entities, usually symbols of some kind. The mathematics 
you were using to talk about the things in the triples is itself a 
language, of course, so when you write
(x,y,z)
you are both using and mentioning a triple. The one you are using is 
linguistic in nature, and might reasonably be claimed to be the 
abstract syntax of the lexical string you wrote (a string of 7 
characters which parses into an abstract entity which is a triple 
containing three one-character lexical entities); but if you were 
using 'x', 'y' and 'z' to refer to, say, backhoes, then the triple 
consisting of three backhoes is most definitely not what is usually 
thought of as an expression in a language. BNF is about *character* 
strings, not sets of sets of backhoes, and the labels of nodes in an 
RDF graph are URIs, not backhoes, right? Things that can be sent 
along wires, using transfer protocols.

It may be that RDF is predicated on a much more revolutionary idea 
about the nature of language than I had previously realized. Do you 
really want to claim that an RDF graph consists of triples of 
*anything*, even of physical things? So for example the triple 
containing me, my cat Henry, and my left arm, in that order, is legal 
RDF? If so, I will need to go away and think about this a little more.

Pat

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Received on Tuesday, 4 September 2001 15:38:45 EDT

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