@Override
    public void startDocument() throws SAXException {
        super.startDocument();

        startPrefixMapping("rdf", RDF);
        startPrefixMapping("xmp", XMP);

        startElement(RDF, "RDF", "rdf:RDF", EMPTY_ATTRIBUTES);
    }
Starts an XMP document by setting up the namespace mappings and
writing out the following header:
<pre>
&lt;rdf:RDF&gt;
</pre>
tika-core/src/main/java/org/apache/tika/sax/XMPContentHandler.java