Re: [Fwd: Are we elements or animals? (was: Use of fragment identifiers in XML)]

>FYI...
>
>-------- Original Message --------
>Subject: Are we elements or animals? (was: Use of fragment identifiers in XML)
>Resent-Date: Thu, 31 Oct 2002 18:45:15 -0500 (EST)
>Resent-From: www-tag@w3.org
>Date: Thu, 31 Oct 2002 17:45:12 -0600
>From: Aaron Swartz <me@aaronsw.com>
>To: Dan Connolly <connolly@w3.org>
>CC: Dan Brickley <danbri@w3.org>, Brian McBride 
><bwm@hplb.hpl.hp.com>,  "Simon St.Laurent" <simonstl@simonstl.com>, 
>www-tag@w3.org,   Chris Lilley <chris@w3.org>
>
>
>On Thursday, October 31, 2002, at 05:07 PM, Dan Connolly wrote:
>>  But I'm sure I've seen test cases where this one matters. [...] But I
>>  can't seem to bring it to mind. It was something about using the same
>>  URI in XLink and RDF, in such a way that the XLink seems to refer to
>>  an element and the RDF seems to refer to what the element is talking
>>  about.
>
>Are you thinking of XPointer?
>
>RFC2396: "The semantics of a fragment identifier [...] is dependent on
>the media type \[RFC2046\] of the retrieval result."
>
>RFC2046: "Additional character sets may be registered with IANA."
>
>http://www.iana.org/ -> http://www.iana.org/numbers.html ->
>http://www.iana.org/assignments/media-types/index.html ->
>http://www.iana.org/assignments/media-types/application/ which says:
>
>"xml [is registered in] \[RFC3023\]"
>
>RFC3023:
>     XML Pointer Language (XPointer)", attempts to define fragment
>     identifiers for text/xml and application/xml.  The current
>     specification for XPointer is available at http://www.w3.org/TR/xptr.
>
>http://www.w3.org/TR/xptr -> http://www.w3.org/TR/xptr-framework/ which
>now has weasel words about RDF and SOAP, but still says:
>
>"This specification defines [a framework which] is intended to be used
>as a basis for fragment identifiers for any resource whose Internet
>media type is one of text/xml, application/xml,
>text/xml-external-parsed-entity, or
>application/xml-external-parsed-entity."
>
>"The Name identifies a single element in the XML resource by ID"
>
>Conclusion: RDF documents which describe fragments *cannot be safely
>served* as application/xml.

RDF documents do not DESCRIBE fragments. They USE them.

>
>(The W3C serves *all* of its RDF documents with that mime type! All of
>TimBL's carefully RDF-specified ...w3.org...#dogs and ...#cats turn out
>to be elements, not animals.)

There really is no problem here. This is a confusion arising from a 
pun on 'semantics', and I think it is based on a ubiquitous 
use/mention confusion which runs like an underground river throughout 
many of these discussions. Transfer protocols and markup languages 
deal with syntactic entities; they even talk ABOUT syntactic 
entities. Content languages, by and large, tend not to. What words 
like 'semantics' mean in RFC 2369 is not what those words mean in the 
RDF (or any other) MT.

Look, of course what you get when you probe with a fragID depends on 
the media type. Perhaps ...#dog IS an element. It really doesn't 
matter what it IS, just so long as that thing can be transmitted, 
stored and recognized by machines. All that matters is that it is 
something that can be used as syntax: can be used as a name, can be 
used to denote. None of the above citations say anything about what 
anything denotes. What RDF *uses* to denote is up to RDF to specify. 
Nothing outside of RDF can specify what meaning RDF assigns to a 
string of characters containing a hash mark.

Pat Hayes

>--
>Aaron Swartz [http://www.aaronsw.com] "Curb your consumption," he said.


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Received on Thursday, 31 October 2002 19:44:37 UTC