What support does HTML5 provide for semantic markup and Semantic Web technologies?

Question

It seems that, as of right now, there is little to no support in HTML5 for semantic markup using RDFa or Microformats. I've done a little bit of reading, but if I were to start using HTML5 right now, what could I do to support semantic markup (such as microformats) and Semantic Web technologies (such as RDFa)? If I want to utilize these technologies now, should I stick with XHTML?

Answer 1

(Some years have passed …)

For semantically annotating your content in HTML5 documents, you can use Microdata, Microformats, and/or RDFa:

• Microdata is an extension to HTML5, but now merely a W3C Working Group Note (and it will not become a W3C Recommendation in the foreseeable future work started again in 2017: https://www.w3.org/TR/microdata/). It’s still included (and potentially under development) in WHATWG’s HTML Living Standard.

• Microformats (as in class values) are obviously supported as these don’t require any changes to the HTML language. Microformats (as in rel values) are supported as soon as they are registered in their own wiki under existing rel values: HTML5 link type extensions (this is the place where all link types have to be registered for HTML5).

• RDFa is an extension to various markup languages, including HTML5. It can also be used in the form of the subset RDFa Lite. All relevant specifications are W3C Recommendations.

(There is also JSON-LD, but I’m not adding it to the list because it doesn’t integrate with the existing markup, it’s a separate "blob", duplicating the content.)