RE: Use of xml:base of in XHTML family documents

On Tue, 2007-06-26 at 09:47 -0400, Clark, John wrote:

> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
>     "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
> <html xmlns="http://www.w3.org/1999/xhtml" 
> xml:base="http://example.com/foo">
> <body>
>   <a href="bar">Link to bar!</a>
> </body>
> </html>
> Based on that, I had thought that since none of the core XHTML (1.x)
> specifications allowed `xml:base` attributes (and thus did not
> normatively reference XML Base), that `xml:base` would simply be ignored
> in XHTML documents.  

The situation is undefined 'semantically' (per XML Base intro).  It is
clearly defined syntactically (per XML validation).  This is not the
same as a mandate to preemptively ignore xml:base.  I don't see anything
that would justify this - unless XHTML compound languages are *not* XML
dialects but some HTML-specific invention with their own infoset, DOM,
EBNF, and an independent notion of validity.

> Perhaps, however, there is another way to think
> about XHTML documents that use `xml:base` attributes.  Just as MathML
> 2.0 defines the compound language "XHTML 1.1 plus MathML 2.0", one might
> easily define the compound language "XHTML 1.1 plus XML Base"; it
> certainly seems that an author using `xml:base` attributes in XHTML
> documents has just this sort of compound dialect in mind.

Again, I've asked (and it doesn't seem that even Dan has an answer): is
XHTML (and its various compound languages) an XML dialect or something
completely different - which happens to only burrow certain XML
mechanisms: such as well-formedness, validity, etc.?  If they are XML
dialects then if they are not valid (which would be the only criteria
for membership in the XHTML document 'family') they lose whatever
authority XHTML might have over Base URI resolution, etc. and (in
addition) couldn't possibly contribute to any justification for ignoring
xml:base in an XML document that is not an XHTML document.

> If it is indeed the case that `xml:base` attributes extend the
> underlying XHTML semantics, then we've come full circle and my earlier
> reasoning on resolution[0] may be correct.  It also means that we'd need
> to edit the base URI appendix and that test case #svg-in-html-5
> (currently listed in the Pending GRDDL Tests document[1]) is incorrect
> about its output.

My vote would certainly be against the approval of a test that tried to
enforce ignoring xml:base on a (non-XHTML) XML document.  We would be
better off not introducing such a test, IMHO, in the same way we have
been careful (or Jeremey has been careful) to not include a test with
*both* xml:base and XHTML base.  GRDDL can't boil the ocean.

> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
>     "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
> <html xmlns="http://www.w3.org/1999/xhtml" 
> xml:base="/spam/eggs">
> <head><base href="http://example.org/foo/baz"/></head>
> <body>
>   <a href="bar">Link to bar!</a>
> </body>
> </html>

This situation is just about as undefined (from the XHTML perspective)
as an XML document that is just the removal of the xml:base away from
being an XHTML document.  For the same reason(s), we shouldn't have
tests in these categories nor should GRDDL pretend to be able to speak
authoritatively about undefined situations.

-- 
Chimezie Ogbuji
Lead Systems Analyst
Thoracic and Cardiovascular Surgery
Cleveland Clinic Foundation
9500 Euclid Avenue/ W26
Cleveland, Ohio 44195
Office: (216)444-8593
ogbujic@ccf.org


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Received on Tuesday, 26 June 2007 14:27:52 UTC