When an orderBefore(A, B) is performed, an implementation must generate a NODE_REMOVED for node A and a NODE_ADDED for node A. Note that the paths associated with these two events will either differ by the last index number (if the movement of A causes it to be re-ordered with respect to its same-name siblings) or be identical (if A does not have same-name siblings or if the movement of A does not change its order relative to its same-name siblings). Additionally, an implementation should generate appropriate events reflecting the “shifting over” of the node B and any nodes that come after it in the child node ordering. Each such shifted node would also produce a NODE_REMOVED and NODE_ADDED event pair with paths differing at most by a final index.