if ((stack = (Stack)_namespaces.get(prefix)) == null) {
stack = new Stack();
_namespaces.put(prefix, stack);
}
// Quit now if the URI the prefix currently maps to is the same as this
if (!stack.empty() && uri.equals(stack.peek())) return;
// Put this URI on top of the stack for this prefix
stack.push(uri);
_prefixStack.push(prefix);
_nodeStack.push(new Integer(_depth));