RDF documents are also XML documents, so they start with the <?xml?> declaration. These documents also must have a specific root element, <RDF>, which encloses the rest of the document. Because the namespace that you use with RDF is usually given the prefix rdf, you often specify the <RDF> element as <rdf:RDF> like this:
<?xml version="1.0" ?> <rdf:RDF . . . </rdf:RDF>
Also note that RDF documents must use the RDF namespace.