I'm setting up a HTML5 webpage and want to include RDFa. I try checking the syntax with the w3 validator, and check the extracted RDF using the w3 RDFa distiller. When I declare namespaces using xmlns:<ns>="<uri>" the validator complains that the attribute is not allowed there, and the specs say that xmlns is deprecated, but if I try the other suggested prefix="<ns> <uri>" the distiller doesn't discover the RDFa embedded on my page. Which way should I stick to?