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RE: ISSUE-76: If we fixed namespaces, does RDFa still have problems?

From: Toby Inkster <tai@g5n.co.uk>
Date: Tue, 15 Dec 2009 09:25:22 +0000
To: Leif Halvard Silli <xn--mlform-iua@xn--mlform-iua.no>
Cc: "Ennals, Robert" <robert.ennals@intel.com>, Maciej Stachowiak <mjs@apple.com>, "public-html@w3.org" <public-html@w3.org>
Message-ID: <1260869122.32395.154.camel@ophelia2.g5n.co.uk>
On Tue, 2009-12-15 at 04:15 +0100, Leif Halvard Silli wrote:

> I think, to make RDFa "native" to HTML and simple to use, then a
> vocabulary for the HTML namespace could be useful. 
> 
> It should be simpler to use this vocabulary than other vocabularies. 
> Either because it could be used without any prefix at all. 

XHTML+RDFa 1.0 already has this. The default prefix is:

	http://www.w3.org/1999/xhtml/vocab#

And it contains a bunch of terms useful for describing (X)HTML
documents. It has terms like "chapter", "appendix", "contents", "index",
"glossary", "copyright" and "license". CURIEs in the default prefix are
written with an empty first part, e.g. the second CURIE in this
attribute:

	rel="dc:license :license cc:license"

Within @rel and @rev in fact, terms from the current XHTML vocabulary
are treated as case-insensitive keywords, so the leading colon isn't
needed either.

I'd certainly like to see the XHTML vocabulary expand to cover other
terms useful for describing typical XHTML documents. Authorship, dates,
topic/keyword, title and description properties seem natural additions.

The vocab itself can be added to without needing any changes to RDFa,
though the new terms would not be recognised as case-insensitive
keywords by RDFa 1.0 processors.

> These HTML namespace vocabularies would then also be possible to use 
> not only in HTML documents, but also in other mark-up languages.

The SVG Tiny 1.2 Rec (which includes RDFa) unfortunately has little to
say on whether the default prefix and keywords apply to SVG. In my
parser, I decided that these should work the same as XHTML. Hopefully,
clearer guidance to using RDFa in non-XHTML host languages will be one
of the things an RDFa WG will deliver.

When SVG or MathML are used *within* XHTML, I certainly think it's a
good idea to apply the XHTML rules throughout. Switching rules for
document fragments does not seem desirable.

-- 
Toby A Inkster
<mailto:mail@tobyinkster.co.uk>
<http://tobyinkster.co.uk>
Received on Tuesday, 15 December 2009 09:26:09 UTC

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