Can I use RDFa with HTML5?
From the RFDa primer:
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.