- From: <noah_mendelsohn@us.ibm.com>
- Date: Tue, 9 Sep 2008 17:52:41 -0400
- To: "Steven Pemberton" <steven.pemberton@cwi.nl>
- Cc: "Ben Adida" <ben@mit.edu>, "Mark Baker" <distobj@acm.org>, www-tag@w3.org
First of all, thank you Steven for your patience in working through this with me. Steven Pemberton wrote: > On Tue, 09 Sep 2008 02:53:56 +0200, <noah_mendelsohn@us.ibm.com> wrote: > > > As I have mentioned previously on this list, I am trying to wrap up the > > TAG finding on the Self-Describing Web [1], and the major unresolved > > question is whether there is a chain of normative specifications, > > presumably starting with the media type registration for > > application/xhtml+xml [2], that justifies the inference of > RDF triples in > > an XHTML document that uses RDFa. > > Hi Noah. > > The RFC for application/xhtml+xml says > > With respect to XHTML Modularization [XHTMLMOD] and the existence > of XHTML based languages (referred to as XHTML family members) > that are not XHTML 1.0 conformant languages, it is possible that > 'application/xhtml+xml' may be used to describe some of these > documents. > > http://www.ietf.org/rfc/rfc3236.txt Yes. > "RDFa in XHTML: Syntax and Processing" (which uses XHTML > Modularization) > says: > > XHTML+RDFa documents SHOULD be labeled with the Internet Media Type > "application/xhtml+xml" as defined in [RFC3236]. > > and further > > There SHOULD be a @version attribute on the html element > with the value > "XHTML+RDFa 1.0" > > http://www.w3.org/TR/rdfa-syntax/#docconf > > (Note that XHTML+RDFa is the first version of XHTML that > doesn't require a > DTD declaration to identify itself. That notwithstanding, there > is also a > DTD available, since current browsers use the existence of a DTD > declaration to switch itself into Standards Mode). > > And of course, "RDFa in XHTML: Syntax and Processing" also saysit is OK > to extract RDF from such documents. OK. > I hope this meets your requirements. Me too :-), but for the moment I'm afraid I'm not convinced. Let's go step by step. A Web browser has in hand a URI, does an HTTP GET, and in return gets status code 200, Content type: application/xhmtl+xml, and an entity body that proves to be a match to the syntactic requirements of RDFA in XHTML. The author of the browers code is aware of both the specifications you quote above, plus presumably the XHTML 1.0 Recommendation and (although you've previously said it doesn't matter here) XHTML M12N. His/her goal is to prove from those specifications that the RDFa is intended to be interpreted per the RDFa specifications (as opposed to being an accidental match, however unlikely, to the syntax of RDFa). Going step by step: * The media type is application/xhmtl+xml, so RFC 3236 definitely applies. * As you note, the RFC says that "it is possible that application/xhtml+xml" may be used to describe XHTML family languages. OK, but does that say anything about which specification I consult next to determine which of the markup, beyond XHTML itself, is to be interpreted, and how? I'm not sure how signalling that something is "possible" has much normative force, and even if it does, it doesn't tell me much about which specifications to consult next. I could claim that I'd written a second specification giving a different interpretation of the RDFa markup, and I don't see how you'd say that one didn't apply. * You then quote the RDFa Syntax and Processing draft: "There SHOULD be a @version attribute on the html element with the value 'XHTML+RDFa 1.0;". Let's for the moment ignore that it's a SHOULD and consider the case where @version is indeed set this way. Is there something in RFC 3236 or XHTML 1.0 to the effect that "a value in the @version attribute of the HTML element is a key that can be used to identify additional specification(s) that provide normative interpretations for markup beyond that which is standardized for XHTML itself?" As best I can tell, XHTML delegates discussion of the <HTML> element to HTML 4.01, and that in turn says that the version attribute is deprecated! [1] Is there something normative in either XHTML or M12N that says "go looking for a specification that seems to have been written by the authority responsible for the namespace used in the new markup?". So, I'm still missing some crucial connections. To be clear, I'm very supportive of RDFa and am not looking for excuses to make trouble here. I would very much like to find a clean unambiguous story to support the self-describing use of RDFa. That said, my view of "follow your nose" is that the feel is usually: start with specification X; it well tell you that there are cases in which specification Y applies, and that in turn may delegate to specification Z, etc. I'm missing that here. The best I can get is that serving a wide variety of XHTML-family content with application/xhtml+xml is not a violation of RFC 3236 (I.e. it's "possible"). What I'm missing is a clear chain of one specification pointing to the next, telling me what to read to interpret those enhanced formats when they show up. I apologize if I'm being dense here, and thank you again for your patient help! > > Best wishes, > > Steven Pemberton And to you! Noah [1] http://www.w3.org/TR/1999/REC-html401-19991224/struct/global.html#h-7.3 -------------------------------------- Noah Mendelsohn IBM Corporation One Rogers Street Cambridge, MA 02142 1-617-693-4036 -------------------------------------- "Steven Pemberton" <steven.pemberton@cwi.nl> 09/09/2008 07:00 AM To: noah_mendelsohn@us.ibm.com, www-tag@w3.org cc: "Mark Baker" <distobj@acm.org>, "Ben Adida" <ben@mit.edu> Subject: Re: Treatment of RDFa in TAG Finding on Self-describing Web On Tue, 09 Sep 2008 02:53:56 +0200, <noah_mendelsohn@us.ibm.com> wrote: > As I have mentioned previously on this list, I am trying to wrap up the > TAG finding on the Self-Describing Web [1], and the major unresolved > question is whether there is a chain of normative specifications, > presumably starting with the media type registration for > application/xhtml+xml [2], that justifies the inference of RDF triples in > an XHTML document that uses RDFa. Hi Noah. The RFC for application/xhtml+xml says With respect to XHTML Modularization [XHTMLMOD] and the existence of XHTML based languages (referred to as XHTML family members) that are not XHTML 1.0 conformant languages, it is possible that 'application/xhtml+xml' may be used to describe some of these documents. http://www.ietf.org/rfc/rfc3236.txt "RDFa in XHTML: Syntax and Processing" (which uses XHTML Modularization) says: XHTML+RDFa documents SHOULD be labeled with the Internet Media Type "application/xhtml+xml" as defined in [RFC3236]. and further There SHOULD be a @version attribute on the html element with the value "XHTML+RDFa 1.0" http://www.w3.org/TR/rdfa-syntax/#docconf (Note that XHTML+RDFa is the first version of XHTML that doesn't require a DTD declaration to identify itself. That notwithstanding, there is also a DTD available, since current browsers use the existence of a DTD declaration to switch itself into Standards Mode). And of course, "RDFa in XHTML: Syntax and Processing" also says it is OK to extract RDF from such documents. I hope this meets your requirements. Best wishes, Steven Pemberton
Received on Tuesday, 9 September 2008 21:52:00 UTC