RDFa (http://rdfa.info/) is a set of extensions to XHTML being proposed by W3C. RDFa uses attributes from XHTML's meta and link elements, and generalises them so that they are usable on all elements. This allows you to annotate XHTML markup with semant.css. A simple mapping is defined so that RDF triples may be extracted.
How it works
RDFa uses the
class-attribute of XML-Elements for refering to a class in an Ontology written in RDF and/or OWL. The
class-attribute is therefore used instead of the
rdf:type-attribute in RDF. Refering to the ontology is done using the
RDFa introduces new elements to XHTML, namely the
content attributes. With this elements RDF-triples can get represented.