Full disclosure: I’m the chair of the RDFa Working Group and have been heavily involved during the RDFa and Microdata standardization initiatives. I am biased, but also understand all of the nuanced decisions that were made during the creation of both specifications.
Support for the Microdata API has just been removed from Webkit (Apple Safari). Support for the Microdata API was also removed from Blink (Google Chrome) a few months ago. This means that Apple Safari and Google Chrome will no longer support the Microdata API. Removal of the feature from a browser also shows us a likely future for Microdata, which is less and less support.
In addition, this discussion on the Blink developer list demonstrates that there isn’t anyone to pick up the work of maintaining the Microdata implementation. Microdata has also been ripped out of the main HTML5 specification at the W3C, with the caveat that the Microdata specification will only continue “if editorial resources can be found”. Translation: if an editor doesn’t step up to edit the Microdata specification, Microdata is dead at W3C. It just takes someone to raise their hand to volunteer, so why is it that out of a group of hundreds of people, no one has stepped up to maintain, create a test suite for, and push the Microdata specification forward?
A number of observers have been surprised by these events, but for those that have been involved in the month-to-month conversation around Microdata, it makes complete sense. Microdata doesn’t have an active community supporting it. It never really did. For a Web specification to be successful, it needs an active community around it that is willing to do the hard work of building and maintaining the technology. RDFa has that in spades, Microdata does not.
Microdata was, primarily, a shot across the bow at RDFa. The warning worked because the RDFa community reacted by creating RDFa Lite, which matches Microdata feature-for-feature, while also supporting things that Microdata is incapable of doing. The existence of RDFa Lite left the HTML Working Group in an awkward position. Publishing two specifications that did the exact same thing in almost the exact same way is a position that no standards organization wants to be in. At that point, it became a race to see which community could create the developer tools and support web developers that were marking up pages.
Microdata, to this day, still doesn’t have a specification editor, an active community, a solid test suite, or any of the other things that are necessary to become a world class technology. To be clear, I’m not saying Microdata is dying (4 million out of 329 million domains use it), just that not having these basic things in place will be very problematic for the future of Microdata.
To put that in perspective, HTML5+RDFa 1.1 will become an official W3C Recommendation (world standard) next Thursday. There was overwhelming support from the W3C member companies to publish it as a world standard. There have been multiple specification editors for RDFa throughout the years, there are hundreds of active people in the community integrating RDFa into pages across the Web, there are 7 implementations of RDFa in a variety of programming languages, there is a mailing list, website and an IRC channel dedicated to answering questions for people learning RDFa, and there is a test suite with 800 tests covering RDFa in 6 markup languages (HTML4, HTML5, XML, SVG, XHTML1 and XHTML5). If you want to build a solution on a solid technology, with a solid community and solid implementations; RDFa is that solution.