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RE: RDF URI (was issue-58: Scalability of URI Access to Resources

From: Williams, Stuart (HP Labs, Bristol) <skw@hp.com>
Date: Tue, 11 Sep 2007 14:17:43 +0100
Message-ID: <C4B3FB61F7970A4391A5C10BAA1C3F0DDA96A6@sdcexc04.emea.cpqcorp.net>
To: "Pat Hayes" <phayes@ihmc.us>, "Chimezie Ogbuji" <chimezie@gmail.com>
Cc: <www-tag@w3.org>

Hello Pat,

> -----Original Message-----
> From: Pat Hayes [mailto:phayes@ihmc.us] 
> Sent: 07 September 2007 18:32
> To: Chimezie Ogbuji; www-tag@w3.org; Williams, Stuart (HP 
> Labs, Bristol)
> Subject: Re: issue-58: Scalability of URI Access to Resources
> 
> Chimezie Ogbuji wrote:
> > On 9/7/07, Williams, Stuart (HP Labs, Bristol) <skw@hp.com> wrote:

<snip/>

> >>> 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'?
> >>     
> Stuart, the Web isn't a particular interpretation. Its a 
> rather large 'theory' in the logical sense which needs to be 
> interpreted. And (maybe this is what Chimezie means?) if the 
> Sweb hadn't come along, I don't think anything in the entire 
> Web world would have suggested that URIs /denote/ anything at 
> all. What they do is connect you to resources, not denote them.

I see that I need to return to RDF Model theory and learn how to use its
terminology correctly.

What I was trying to express is that the web itself places some
constraints on the 'IS' mapping (from rdf-mt) part of an interpretation
- at least for 'information resources' where I believe that the
intention of WebArch is that URI "denote" the resources to which they
"connect". 

(Ok... and yes there are so many more things in the world than
information resources such that in proportion there are vanisihingly few
of those!)

> > URI's in general denote 'resources' but (formal) denotation IMHO is 
> > only as useful as the inference capabilities it facilitates.  If
this 
> > wasn't the case, there would be no reason to bring KR into the
picture 
> > (i.e., 'the web' + KR = 'semantic 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".
> >>     
> >
> > >From the context.  An unparsed RDF/XML document is nothing more
than
> > an information set, with QNames composed from URIs.  The namespace 
> > names denote 'resources' (per URI RFC), but this denotation is 
> > basically inert: there is no mechanism to guide inference (or 
> > interpretation).
> >   
> Put another way, you have (sound of teeth gritting) 
> denotation but no assertions. You only get inferences made 
> valid when some sentence actually says something ABOUT the 
> denotation. If all you have is the denoting name, then about 
> all you can do is to repeat it more or less loudly.

Ok... but absent the semantic web, people have been saying things
(making assertions about) URI's and the resources to which they are
taken as referring from way before the semantic web. That those
assertion may have been wrong or inconsistent didn't matter one jot to
the web there was little (no?) machinery trying to evaluate their truth.

> > After you parse the document into an instance of the RDF abstract 
> > model, you have a different context and different mechanisms apply
(by 
> > normative specifications).  They are still URIs in the RFC 2396
sense, 
> > but the denotation is no longer inert.
> >   
> I hope/think I see what you mean, but this is a very odd way 
> of putting it. How about: what the RDF gives you is some 
> actual formal assertions about the referent, from which you 
> might be able to draw some new conclusions about it.

That makes sense to me.

> >> 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.
> >>     
> I think it is, in fact. Without the Sweb, all claims about 
> URIs denoting non-information resources is very little more 
> than a TAG fairy story, and about as easy to demolish as any 
> other fantasy.

:-) "Webarch constrains that range of things that can be referred to by
URIs." Is that what you are saying?

I guess I'm prepared to take that at face value, but I'd like to
understand a little more from your pov what induces that constraint. 

Or maybe your saying the constraint exists but that WebArch is not the
instrument which induces it.

Or maybe you're saying that WebArch (the document) only covers the case
for URI that denote/refer/connect to information resources and leaves
(or should leave) the rest open.

> > Note, I said 'primarily'.  Consider that a majority of the 'Good 
> > practice' assertions in AWWW are relevant only to representations.
> >
> >   
> >>> 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.
> >>     
> It is unconstrained, but there is no reason to suppose that 
> it is possible. Take the entire Web pre-RDF, and tell me 
> where there is ANYTHING in its architecture or usage which 
> requires a URI to denote/identify/have any meaningful 
> relation to anything other than an information resource. 

I don't think I can! Not that "requires". 

Can you point to ANYTHING which prevents it (that URI "..have a
meaningful relation with anything other than an information resource.")?

> The 
> fact that some Web pioneers had wet dreams about 
> revolutionizing the Nature of Meaning doesn't tell us 
> anything about anything other than psychology and ambition.

Hmmm... I think that's a little unkind. Just to be clear I wouldn't
place myself in the ranks of such a category - I'm a "johnny come
laterly" in these circles. I think that it more the case that people
have wanted to apply "the Nature of Meaning" in a web context - and
perhaps a large number of us are learning how little we know (certainly
true for me).

> Pat

Regards,

Stuart
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Registered No: 690597 England
Received on Tuesday, 11 September 2007 13:20:39 UTC

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