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="
http://creativecommons.org/licenses/by-sa/3.0/us/" > >Creative >
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
- 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:
- 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_Presid... [2]http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1000275 [3]http://drupalrdf.openspring.net/node/106