In rules parlance, a situation is a position along with the information about who moves first from that position. See situational superko.
However in normal parlance (reviewing a game, etc) a situation can have meaning similar to that of position.
What about a possibility of taking a ko? According to presented definition, two positions with the same arrangement of stones and the same side to move, differing only by last ko capture, would be treated as identical.
Hash keys in chess programs (I write one) take into account castling rights as well as the possibility of en passant capture. The same ist true about commonly used FEN format. If this analogy is correct, then situation should also take into account the ko point (if any).
Bill: There is something of a logical problem with that. Since situation is used to determine which plays are banned, how can it depend upon which plays are banned?
Dave: Since the bans depend on what has happened in the past, if "situation" does not consider such information, don't we need another term = situation + other information?