// The URI reference may be relative. The base URI (see [3.2 Base URI])
// of the node in the second argument node-set that is first in document
// order is used as the base URI for resolving the
// relative URI into an absolute URI.
XObject arg2 = arg1Expr.execute(xctxt);
if (XObject.CLASS_NODESET == arg2.getType())
{
int baseNode = arg2.iter().nextNode();