Henri Sivonen wrote:
The above
could be marked up in RDFa, with pre-defined vocabs, like so:
It should be noted that the concept of "pre-defined vocabs" is neither
in the HTML+RDFa draft nor in the RDFa in XHTML spec from the XHTML2 WG.
When I said "pre-defined vocabs", I was refering to "using xmlns: at the
top of the document to declare prefixes that will be used in the rest of
the document". I was specifically referring to technology that already
exists as a W3C Recommendation.
Henri Sivonen wrote:
<p
about="EmeryMolyneux-terrestrialglobe-1592-20061127.jpg" >
typeof="dctype:StillImage"> > <span
property="dc:title">Emery Molyneux
Terrestrial Globe</span> > by <a rel="cc:attributionUrl"
href=" >
http://example.org/bob/" > >
property="cc:attributionName">Bob
Smith</span> > is licensed under a <a rel="license" >
href="
Commons Attribution-Share Alike 3.0 United States License</a>.</p>
Hiding the CURIE declarations is a common pattern when advocating RDFa:
It makes RDFa appear tidier than it is. To write this in RDFa in XHTML
(the RDFa spec you say is safe to use for deployment), one would need
to declare the CURIE prefixes:
It is a common pattern because deployment experience has shown us that
prefix declaration usually happens once, at the top of a document. See
the source for Digg[1], The Public Library of Science[2], Drupal 7[3]
for examples of how this is done on live sites today.
This is orthogonal to how web authors include scripts and CSS at the top
of their documents.
Henri Sivonen wrote:
However -
XHTML1+RDFa is a published W3C Recommendation and it is safe
to use it for
deployment.
RDFa in XHTML has indeed been published as a Recommendation jointly
by the Semantic Web Deployment Working Group and the XHTML2 Working
Group. However, you fail to mention that even though the document mentions
"HTML" in its first sentence, all the normative matter concerns strictly
XHTML and the document has gone through the W3C Process as a specification
that applies to XML.
RDFa was designed to work in XHTML and HTML. The RDF in XHTML Task
Force, which produced XHTML1+RDFa, was only chartered to realize the
language in XHTML. Had we been chartered to work on HTML5, which wasn't
even an official W3C work product at the time, we would have done so.
We are currently working on ensuring that markup in both XHTML and HTML
remains identical so that all XHTML1+RDFa will continue to be
interpreted properly in HTML5.
Henri Sivonen wrote:
MediaWiki uses the text/html and, thus, its pages get
processed as HTML,
so it would be inappropriate to rely on a spec that had been reviewed
as an XML spec.
MediaWiki's pages only get processed as HTML by web browsers. The Web is
more than web browsers - search engine companies, for example, often
process the document based on the received DOCTYPE. While that document
is served as "text/html", it is validated as XHTML 1.0 Transitional by
the W3C.
It is a goal of the RDFa Working Group to ensure that any document that
is XHTML1 valid, served as "text/html", produces the same triples as if
it were served as "application/xhtml+xml". As a general rule, that is a
goal that the current parsers meet and that we will ensure to codify in
HTML5+RDFa.
Henri Sivonen wrote:
Furthermore, the ease of getting a spec to REC at the
W3C depends on how
many people are interested in the spec. The more people are interested
in a spec, the more review comments there are. The flip side is that when
there's *less* interest in a spec, it's easier to get it to Recommendation
due to fewer comments raised. Thus, progress along the REC track isn't a
commensurable indicator of technical merit or technical maturity across
different specs and WGs.
This is a red herring - any published technology will always have
detractors that don't like it and claim such things as "well, I wouldn't
call that a spec because of personal opinion X.". XHTML+RDFa is a REC,
and because it is a REC, we can speak with authority that the spec is
not going to change and can be used as-is.
XHTML+RDFa had a great deal of review - just check the mailing list
reviews and number of implementations (over 8 at last count). The fact
that there are people using RDFa and so few errata for the XHTML+RDFa
spec thus far is proof of the substantial review that it underwent.
Rather than argue the same FUD for Microdata, which anybody could, I
suggest that we focus on technical merits.
Henri Sivonen wrote:
Also, when assessing the "safe"
deployability of RDFa in XHTML, it's
relevant to consider that
1) RDFa in XHTML was knowingly (see
http://lists.whatwg.org/pipermail/whatwg-whatwg.org/2008-August/015913.html)
progressed on the Recommendation track without resolving how RDFa works
with HTML first.
Not True. We were very aware of HTML4 - but were not chartered to work
on HTML5. How RDFa would work in HTML4 was brought up and considered
frequently. HTML5 was barely on the radar for most of RDFa's
development. We even went as far as developing a DTD for HTML4+RDFa -
but there was no avenue to publish it at W3C since all work on HTML4 had
ceased.
The fact that you can point fully-conforming Javascript RDFa processors
(such as ubiquity-rdfa or rdfquery) at an HTML4 or HTML5 document
containing RDFa and get data out is proof that we went out of our way to
ensure a universal markup mechanism for semantic data.
Keep in mind that when RDFa was being developed, HTML5 wasn't even a W3C
work product. Now that it is, we have an updated HTML5+RDFa spec (which,
by the way, hasn't required a single change to the RDFa processing rules).
Henri Sivonen wrote:
2) An RDFa 1.1 is in the works, and the changes
being considered make RDFa 1.0 look like a beta release. (Which is
understandable, since a good part of the technical review of RDFa has
occurred after RDFa in XHTML was rushed to REC.)
This is FUD. You are asserting your opinion without making any sort of
technical argument. The larger changes being considered are feature
additions. Let's stick to the technical arguments that will impact
Wikipedia rather than devolve into how each of us view the ridiculously
convoluted process that got RDFa and Microdata to where they are today.
Automatic XML Literals are the only thing that may not be
backwards-compatible in RDFa 1.1, and Wikipedia can guard against this
by ensuring that they follow this one rule:
* If you want to express any data as an XML Literal, make sure that you
use datatype="rdf:XMLLiteral".
All other changes are feature additions based on community requests -
some of which, both Aryeh and you requested. :)
-- manu
[
1]http://digg.com/politics/Barack_Obama_Officialy_Becomes_44th_American_Preā¦
[
2]http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1000275
[
3]http://drupalrdf.openspring.net/node/106
--
Manu Sporny (skype: msporny, twitter: manusporny)
President/CEO - Digital Bazaar, Inc.
blog: Monarch - Next Generation REST Web Services
http://blog.digitalbazaar.com/2009/12/14/monarch/