Dan Brickley wrote:
... I guess the fact that @property is supposed to be CURIE-only
isn't a
problem with parsers since this can be understood as a CURIE with
no (or
empty) substitution token.
Actually, most RDFa parsers will break if full URIs are used in RDFa
attributes: in RDFa all CURIEs need a prefix which is a string of
zero or more alphanumeric characters, dashes and hyphens followed by
a colon (and yes, the empty string is allowed - but it is permanently
bound to <http://www.w3.org/1999/xhtml/vocab#>). The proposed
recommendation (IIRC, that's the current status) for CURIEs *does*
actually allow for unprefixed CURIES, but RDFa enforces extra
conditions. (As it was published before the CURIE spec, which is a
spin-off of RDFa.)
A suggestion I've heard for using full URIs is:
<html xmlns:http="http:">
<title property="http://purl.org/dc/terms/title";>Foo</title>
</html>
Which should theoretically work according to the reference algorithm
in the RDFa syntax document, however it does (I believe) break the
XML Namespaces spec. (Though that wouldn't be a problem if an
alternative, non-xmlns, syntax were adopted for CURIE prefix
binding.) It wouldn't surprise me if a few RDFa parsers had issues
with this caused by the front-end XML parser they use.
So RDFa, as it is currently defined, does need a CURIE binding
mechanism. XML namespaces are used for XHTML+RDFa 1.0, but given that
namespaces don't work in HTML, an alternative mechanism for defining
them is expected, and for consistency would probably be allowed in
XHTML too - albeit in a future version of XHTML+RDFa, as 1.0 is
already finalised. (I don't speak for the RDFa task force as I am not
a member, but I would be surprised if many of them disagreed with me
strongly on this.)
Back to when I said "most RDFa parsers will break if full URIs are
used in RDFa attributes". The Perl library RDF::RDFa::Parser doesn't,
so if you want to do any testing with full URIs, it can be found on
CPAN. Full URIs are a pain to type though - I certainly prefer using
CURIEs.
--
Toby A Inkster
<mailto:m...@tobyinkster.co.uk>
<http://tobyinkster.co.uk>
