On Jan 11, 2009, at 14:01, Toby A Inkster wrote:
RDFa *does not* rely on XML namespaces. RDFa relies on eight
attributes: about, rel, rev, property, datatype, content, resource
and typeof. It also relies on a CURIE prefix binding mechanism. In
XHTML and SVG, RDFa happens to use XML namespaces as this mechanism,
because they already existed and they were convenient.
Convenience is debatable. In any case, it is rather disingenuous to
say that RDFa doesn't rely on XML Namespaces when all that has been
defined so far relies of attributes whose qname contains the substring
"xmlns".
In non-XML markup languages, the route to define CURIE prefixes is
still to be decided, though discussions tend to be leaning towards
something like:
<html prefix="dc=http://purl.org/dc/terms/ foaf=http://xmlns.com/foaf/0.1/
">
<address rel="foaf:maker" rev="foaf:made">This document was made by
<a href="http://joe.example.com"; typeof="foaf:Person"
rel="foaf:homepage" property="foaf:name">Joe Bloggs</a>.</address>
</html>
Unless this syntax were also used for XHTML, the above would be in
violation of the DOM Consistency Design Principle of the W3C HTML WG.
This discussion seems to be about "should/can RDFa work in HTML5?"
when in fact, RDFa already can and does work in HTML5 - there are
approaching a dozen interoperable implementations of RDFa, the
majority of which seem to handle non-XHTML HTML.
Those implementations violate the software implementation reuse
principle that motivates the DOM Consistency Design Principle. (The
software reuse principle being that the same code path be used for
both HTML and XHTML on layers higher than the parser.)
The prefix mapping mechanism of CURIEs has been designed with
disregard towards this software reuse principle (in use in Gecko,
WebKit and, I gather, Presto) that should have been known to anyone
working on Web-related specs far before "DOM Consistency" was written
into the Design Principles of the HTML WG.
--
Henri Sivonen
hsivo...@iki.fi
http://hsivonen.iki.fi/
