RDF (Resource Description Framework) Question:

Until recently, it was not possible to incorporate full RDF into XHTML without violating the validity of the resulting XHTML, except for the usage of the meta and the link elements in the header. The best solution was to store the RDF separately and use the URIs to refer to the XHTML page and the link element in the XHTML page to refer to the RDF content. This technique is often called an RDF autodiscovery link and is used by a number of tools already. However, this has changed with the newer developements of GRDDL and of RDFa. The GRDDL provides a bridge to the microformats approach while RDFa provides an XHTML1.1 module that gives the possibility to use virtually any RDF vocabulary as annotations of the XHTML content, yielding RDF data.