Here, <res:binding> should be closed immediately after giving a value
for the rdf:nodeID attribute. It is invalid, but NullPointerException is
Any chance of rebranding the validator as the W3C RDF*/XML* validator?
RDF/XML and RDF are not the same thing, and conflating them is bad.
There are many other syntaxes available for RDF which are not supported
here. (Being a bit pedantic, but hey...)