The spec mentions the use of XHTML5 elements inside other XML-based
document formats. However, the use of foreign namespaces inside
XHTML5 is not covered.
The obvious candidates for compound document mixing are SVG and
MathML. Also, there are indications that people will want to embed
RDF metadata in documents even though the syntax of RDF is designed
for external metadata and isn't really all that good for embedded
metadata. I think WA 1.0 should give some guidance on these matters.
Where should the svg element from the SVG namespace be allowed in an
XHTML5 host document? (My expectation: It should be allowed at least
everywhere where the img element would be allowed. There may be good
arguments for allowing svg as block as well.)
Where should the math element from the MathML namespace be allowed in
an XHTML5 host document? (My expectation: It should be allowed where
strictly inline level content is allowed. My understanding is that
also display math has inline semantics even though it has a blockish
presentation.)
Where should the RDF element from the RDF namespace be allowed in an
XHTML5 host document? (My expectation: It should be allowed as a
child of the head element. Other metadata goes there and the contents
of head are hidden in legacy browsers, so the text node descendants
of the RDF element from the RDF namespace won't leak to presentation
in legacy browsers. Also, if conformance checkers don't have a hole
that allows embedded RDF, people who want to embed RDF will come up
with worse workarounds to avoid eliciting errors in conformance
checking. To work around the fact that RDF envelope is designed for
external metadata and not embedded metadata, XHTML5 should probably
suggest that authors use rdf:about="" to refer to the current
document as per XMP*.)
And then something more controversial:
Should an XHTML5 conformance checker allow arbitrary foreign elements
as children of the head element in order to allow free
experimentation with invisible non-RDF metadata in a way that doesn't
encourage experimenters to put their stuff inside comments or
something equally ugly?
* http://partners.adobe.com/public/developer/en/xmp/sdk/
XMPspecification.pdf page 23
--
Henri Sivonen
[EMAIL PROTECTED]
http://hsivonen.iki.fi/
