XPathEvaluator

XPathExpression createExpression(
    in DOMString expression, 
    in XPathNSResolver resolver) raises(core::DOMException); 

XPathNSResolver createNSResolver(
    in Node nodeResolver); 

XPathResult evaluate(
    in DOMString expression, 
    in Node contextNode, 
    in XPathNSResolver resolver, 
    in unsigned short type, 
    in XPathResult inResult) raises(DOMException);