String value = null;
Document d = getVerifierContext().getDocument();
if (d==null) return null;
XObject result = XPathAPI.eval(d, xpath,
(PrefixResolver)new XpathPrefixResolver (d));
NodeList nl = result.nodelist();
for(int i=0; i<nl.getLength();i++){
Node n = ((Node)nl.item(i)).getFirstChild();
if (n==null) return null;
value = n.getNodeValue();
}