Re: XML Schema draft populates the intersection of Language and InformationResource [ISSUE-14 httpRange-14]

On 9/28/07, Richard Cyganiak <richard@cyganiak.de> wrote:
> Chimezie,
>
> On 28 Sep 2007, at 23:05, Chimezie Ogbuji wrote:
>
> > On 9/28/07, Richard Cyganiak <richard@cyganiak.de> wrote:
> >>> Well, I'm not sure it follows that it 'clearly' identifies a section
> >>> in the HTML case - unless you are using the web-arch notion of
> >>> 'identifies' and not denotation but even so...
> >>
> >> *Of course* I'm using the web-arch notion of "identifies".
> >
> > Okay then, you are comparing apples to oranges.  Saying RDF
> > 'identifies' things is an abuse of notation as far as I'm concerned.
>
> The terms "denote", "identify", "indicate" and "mean" are used
> interchangeably throughout the RDF specs. It's unfair to blame me for
> this.

You're right, that would be very unfair :).  I'm not blaming you in
particular, but the *general* way in which (semiotic) denotation and
web architecture's notion of identification are used interchangeably
(in more places than just in the RDF specifications).

In the long run, the ramifications for this abuse of notation are
significant in my opinion but hard to articulate in the short term.
They are the result of an impedance between web architecture and KR
that is being systematically ignored.

> The mechanism by which fragment URIs in RDF *identify* (not my choice
> of term) are spelled out quite clearly in section 7 of rdf-concepts [1].

I would argue that that particular section only attempts to reconcile
RDF's use of URIs with RFC 2396 and that (in practice) the
authoritative mechanism is the one outlined in rdf-mt since it is
based on a framework (model-theory) that doesn't punt on the notion of
reference.

> Is there really that much of a disconnect?

Yes.  Consider (as I've suggested before) if
http://www.ihmc.us/users/phayes/PatHayes.html had a @profile which
authoritatively identified a way to render the information about that
page in RDF.  If the RDF included assertions that the 'thing' denoted
by that URI is something that clearly cannot emit representations over
the wire don't we then have a conflict?

> URIs are governed by a paper trail of RFCs, starting at RFC 3986 and
> leading through the IANA scheme and media type registries, then
> through the RFCs for the different URI schemes such as http: and urn:
> and tag:, and through a whole bunch of media type registrations, and
> from there it bottoms out at specific data format specs such as those
> for HTML and RDF. Thus, webarch gives us a framework that defines URI-
> space

.. snip ..

> That's the framework within which RDF has to operate.

With regards to those things that web-arch is *primarily*  concerned
with, yes.  However, this is but a small subset of useful referents.
If RDF's "universe of discourse" is restricted and dictated by web
architecture, this would result in a Semantic Web which would have
*zero* value for facilitating scientific research, for instance.

> In terms of rdf-
> mt, I take this to mean that the denotation of many URIs (those that
> have representations, according to httpRange-14) is fixed by the Web.

Again, this makes for a very impotent knowledge representation.

> There is a school of thought that wants to see URI-space as a blank
> slate for the purposes of RDF, completely disconnected from the role
> of URIs on the Web.

I consider myself part of that 'school of thought', however, I would
add the caveat that where RDF URIs are used to describe the things for
which web-arch has an unambiguous operational framwork (so called
'information resources'), then they should adhere to web-arch best
practices (and shouldn't be 'disconnected').

However, for everything else it is fair game to think of URIs as
nothing more than semiotic symbols.  Anything less, is  abuse of
notation, short-sighted, and more of a threat to SW adoption than
anything else (especially if we are serious about inference being part
of the SW value proposition).  I don't mean to sound harsh (and again,
this criticism isn't directed at you), but I don't know any other way
to characterize the notion that RDF denotation is completely bound by
web-arch.

> Personally, I have trouble seeing the advantage
> of this view.

If you consider my modification to this view as you described it, the
advantage is profound IMHO (and is the 'real' value proposition of the
SW).  You can use RDF to denote 'things' that have representations
that live in a transport protocol with very well-engineered
operational semantics.  You can further augment these operational
semantics with 'unambigous' assertions that are much more expressive
than what web-arch alone can describe.  You can do so in a way that is
consistent between intelligent agents, simple web agents, and human
consumers.

And (the icing on the cake) you can make assertions about other things
which do not live in the transport layer (so to speak).  I would argue
that with respect to KR, this larger class of referents is much more
relevant.

The only thing required is to drop the idea that web-arch is
sufficiently expressive (by itself) to facilitate inference about the
nature of a referent.  It simply is not built to do that.

> If you want to operate in a universe parallel to the
> Web, then why use URIs in the first place? Why not simply use KIF or CL?

Because you can have your cake and eat it too - all that is required
is a compromise to leave denotation to KR where it belongs.

> (Although, in defense of the "parallel universe" school, this view is
> legitimized by a passage in rdf-mt [2], which, it appears, directly
> contradicts rdf-concepts [1].)

Which particular passage do you have in mind?

-- Chimezie

Received on Saturday, 29 September 2007 00:47:31 UTC