Smil 3.0 validation error using metadata element

Hi-

The w3 SMIL 3.0 site gives examples of adding rdf content to the metadata tag:
http://www.w3.org/TR/smil/smil-metadata.html#edef-metadata

However, these examples do not validate with the DTD provided:
SMIL30Language.dtd from http://www.w3.org/TR/smil/DTD.zip

This DTD defines the metadata element as an empty element. Sorry if I'm missing something basic. Please let me know if I should be asking elsewhere.

Thanks-

Michael Vandermillen
Digital Library Software Engineer
Office for Information Systems
Harvard Library
90 Mt. Auburn St.
Cambridge, MA 02138
978-495-3724
michael_vandermillen@harvard.edu