centralized project, inventing custom microformats is discouraged
will not scale, valid for a small number of microformats
RDF/A
freely extensible
All resource descriptions can be extracted
RDF-focused
W3C-supported
Was not XHMTL 1.0 compliant until Recommendation October 2008
Neither are standard practice at the moment but some browser support appearing
Microformats is mainly a valid extension in the use of the class attribute
RDF/A extends a valid XHTML document by adding either new XHTML attributes or values or uses XHTML elements in invalid places
(meta element in the body of a document
RDF/A approach and Microformat approach will be supported in XHTML 5
