Can I use RDFa with HTML5?
From the RFDa primer:
To date, because XHTML is extensible while HTML is not, RDFa has only been specified for XHTML 1.1
Now it’s 2013 and two weeks ago the W3C published HTML+RDFa 1.1: Support for RDFa in HTML4 and HTML5 as Recommendation:
This specification defines rules and guidelines for adapting the RDFa Core 1.1 and RDFa Lite 1.1 specifications for use in HTML5 and XHTML5. The rules defined in this specification not only apply to HTML5 documents in non-XML and XML mode, but also to HTML4 and XHTML documents interpreted through the HTML5 parsing rules.
So yes, you can use RDFa in HTML5.
There is a draft spec for RDFa in HTML5, but at present I'm not aware of any way to validate the results. The main obstacle for using RDFa in straight HTML5 is that there is no support for namespaces under HTML5 parsing rules.
Today I came across the up to date version of that spec, RDFA in HTML.