Effectively, there are eight (nine, if one adds our proposed Rule 6) fully independent explicit Sequence Rules: 1a, 1b, 2, 3, 4a, 4b, 4c, and 5. The fact that these are not "Sequence Rules 1-8" is simply a result of the historical evolution of the Sequence Rules. "Exhaustively" simply means "until a decision is reached, or it is determined that no such decision is possible."