RDFa 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 semantics. A simple mapping is defined so that RDF triples may be extracted.
The RDFa extension allows you to extract and detect RDFa in Firefox. The addon is cross-platform and it works on Mac OS X, Windows and Linux.
