public Sequence eval(Sequence contextSequence, Item contextItem) throws XPathException {
if (contextSequence == null || contextSequence.isEmpty()) {
// if the context sequence is empty, we create a default context
final RootNode rootNode = new RootNode(context);
contextSequence = rootNode.eval(null, null);
}
final Sequence[] args = getArguments(null, null);
final Item item = args[0].itemAt(0);
QNameValue qval;