{
Hashtable usedrefs = null;
DTMIterator ni = arg.iter();
int pos;
UnionPathIterator upi = new UnionPathIterator();
upi.exprSetParent(this);
while (DTM.NULL != (pos = ni.nextNode()))
{
dtm = xctxt.getDTM(pos);
XMLString ref = dtm.getStringValue(pos);