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RE: ISSUE-58: Scalability of URI Access to Resources

From: Williams, Stuart (HP Labs, Bristol) <skw@hp.com>
Date: Fri, 7 Sep 2007 11:38:45 +0100
Message-ID: <C4B3FB61F7970A4391A5C10BAA1C3F0DD35294@sdcexc04.emea.cpqcorp.net>
To: "Chimezie Ogbuji" <chimezie@gmail.com>
Cc: <www-tag@w3.org>

Hello Chimezie,

So... I'm going to be a little obtuse, maybe deliberately so... but
maybe I should also make it clear what is bugging me, which is the use
of the prefix RDF in the term "RDF URI"... they are just URIs... I don't
see what insisting on calling them "RDF URI" buy's you.

> On 8/28/07, Williams, Stuart (HP Labs, Bristol) <skw@hp.com> wrote:
> > Hello Chimezie,
> >
> > Probably  couple of obtuse questions...
> >
> > - How do "RDF URI" differ from URI in general?
> 
> I tried to cover some of this in the following Wiki:
http://esw.w3.org/topic/RDFSemiotics

I'm afraid that didn't help me :-(. I certainly understood the semiotic
triangle stuff and have been exposed to it before.

As 'symbol' what makes "RDF URI" (your term)  different from URI in
general.

> This is mostly a rehash from http://www.w3.org/TR/rdf-mt/ (so 
> I hope Pat will slap me on the hand when I'm chatting 
> rubbish), but generally, RDF URIs are 'symbols' which denote 
> things in an interpretation (a 'theory').

And URI in general do not? Even in the particular interpretation that we
might commonly call 'the web'?

> The expressions in 
> which the RDF URIs are used describe a set of conditions that 
> must be met to satisfy the interpretation.  The end-game 
> (goal, if you wish) is "to provide a technical way to 
> determine when inference processes are valid, i.e.
> when they preserve truth."

I don't understand how I can tell whether or not I'm using an "RDF URI".
OTOH, I can tell when I'm using a URI in RDF (or HTML or an email or...)

> The main difference is that the domain of discourse is a 
> superset of what Web architecture is primarily concerned 
> with: information resources and their representations.  

Though I think Pat would wish it otherwise, I don't think that in terms
of the denotation of URIs, the domain of discourse in Web Arch is
constrained in the way that you describe.

> Whereas in a model-theoretic language, the 'semantics' are 
> determined from the expressions which make use of the RDF 
> URIs, Web architecture is (or it seems that way from the 
> specific best practices in AWWW) primary concerned with the 
> consumption of information resources to meet a different 
> goal: a user browsing a page, or a web crawler browsing pages 
> to create indices for subsequent searching.

Hmmm.... I'll think about that. There is a particular artiefact, AWWW, a
document which is an expression of a set of principles and best
practices that we could agree on (at the time). However, there is the
much larger conceptual artifact of "The Architecture of the Web". Whilst
AWWW speaks mostly of what it calls "information resources" the scope of
what URIs can (and I'll use the word here risking a blast from Pat)
identify (by which I mean 'refer-to') is unconstrained by AWWW.

> In addition, outside of the consumption of information 
> resources, there is no 'formal' mechanism to follow to 
> 'interpret' or infer 'meaning' from web resources (other than 
> specific representation formats - which are primarily 
> concerned with syntax not 'semantics' )
> 
> > - How would a recognise that a given URI is an "RDF URI"?
> 
> By the context of its use.
> http://metacognition.info/profile/webwho.xrdf#chime is the 
> URI I've 'minted' to represent me.  

ok...

> When used as a link in an 
> HTML document, it is simply a (typed) link to my FOAF 
> document.

Hmmm... less ok... assuming that you are serving as
"application/rdf+xml" the by virtue of the RDF media type definition
that is still a reference to you, the person, rather than a bit of text
in an RDF/XML representation of a graph - or more accurately it is a
reference to a/the thing in an intepretation which statisfies the
assertions made in the graph (which in all probability is you).

ie. that that reference is made in an HTML document has not changed the
intended referent of the URI.

>  When parsed by an RDF 'agent' - from that FOAF 
> (RDF) document - it is understood to 'denote'
> Chimezie Ogbuji (me).  

And somehow the intended referrent is/or may be different if parsed from
an HTML representation? IMO that is *not* an intention of Web
Architecture.

FWIW: I believe that "unique denotation of URI" is an intention the
design of Web Architecture; I am equally aware that such a position
denies "context of use" as a means to disambiguate the referrents of
referring expressions. I am equally aware that in general the context in
which a referring expression occurs can be significant. I have never
been able to square that circle - though the closest I have come is to
regard the web as one big context and referrents of references made
using URI as invariant within that (large) context. It seems like a
design choice in the design of Web Architecture - it is I think the
place where the constraints of the Web apply to the semantic web. 

> So, the expressions which make use of 
> this URI are the constraints which apply in order to meet the 
> interpretation expressed in that FOAF graph.
> 
> >
> > Thanks,
> >
> > Stuart Williams
> > --
> > Hewlett-Packard Limited registered Office: Cain Road, 
> > Bracknell, Berks
> > RG12 1HN
> > Registered No: 690597 England

Thanks,

Stuart
<snip/>
> 
Received on Friday, 7 September 2007 10:41:12 UTC

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