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

From: Chimezie Ogbuji <chimezie@gmail.com>
Date: Fri, 28 Sep 2007 15:41:38 -0400
Message-ID: <f6ec8dcb0709281241o760f2740jccbacba0453a2d6@mail.gmail.com>
To: www-tag@w3.org
Cc: "Richard Cyganiak" <richard@cyganiak.de>

Richard Cyganiak writes:
>On 28 Sep 2007, at 20:24, Dan Connolly wrote:
>> The 303 redirect stuff is almost always more trouble than it's worth.
>> I can't think of any cases other than legacy when I'd recommend it.
>> Using doc#term is much more straightforward.
>I'm surprised to hear that.

> As I understand it, <doc#term> without 303 can't handle content negotiation.

Is this really such a bad thing? I think of content negotiation as
nothing more than additional mechanism for client/server handshaking
and not a *necessary* component for well-engineered, RESTful ('Cool')
URIs.

> If RDF is served at <doc>, then <doc#term> identifies whatever the RDF says about it (so it could be anything). If HTML is served at <doc>, then <doc#term> clearly identifies a section of an HTML document.

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...

As I understand it, the 200 response (as well as the payload recieved)
is a protocol-level cue to the 'nature' of <doc> but not <doc#term>.
It is the web client that interprets the frag Id as a visual cue for
shifting focus, but this is heuristic at best and certainly not more
authoritative than an assertion in RDF such as:

<doc#term> rdf:type <html:fragmentIdentifier>

> To me, that seems like an unacceptable ambiguity.

I don't agree.  The ambiguity (IMHO) is due to the fact that nothing
authoritative can be inferred about what is 'denoted' by the frag
identifier from an HTML representation alone, whereas (in the case of
RDF), an authoritative conclusion about what is denoted *can* be
reached (with the right assertions) since RDF is a KR and HTML is not.

> A 303 from <doc> to <doc.rdf> and <doc.html> is needed to resolve this.

That's one approach.  Note, however, this can also be resolved without
the need for protocol-level trickery (which doesn't even contribute
any additional cues to the nature of the <doc#term>): <doc> can
respond with an HTML reprsentation which has an authorized mapping to
RDF (via GRDDL).  The GRDDL result can include 'authoritative'
assertions about <doc#term>.

> So, are you saying that content negotiation is not worth the trouble,  or that the ambiguity doesn't matter?

I can't speak for Dan, but I'd say it is not worth the trouble - at
least for scenarios where the problem being addressed is providing
both human and machine readable content from the same URI

-- Chimezie
Received on Friday, 28 September 2007 19:41:48 UTC

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