schema.org is an Initiative initialized by big Search Engines Bing, Google and Yahoo [http://schema.org/docs/full.html]. The Goal is to bring Semantic Markup on propertary HTML5 Microdata Schemata. There is a small number of extensible Formats. This can be mapped to RDF without problem.
RDF mapping available.
extends Micradata Vocabulary with proprietary Category Hierarchies:
With RDFa one can encode anythin one wants and use any Vocabulory that is around there and one has not to relay on specialized predefined Vocabularies.