Of course, when you checkmate your opponent, he may well point it out. You may well observe it. An arbiter may observe it. What I was hinting at, was the Heidenfeld principle. Wrong things can happen, quite amusingly, and only be noticed after the event. Now, if a flag has fallen, it will remain fallen in later moves, and this can be observed. It does not necessarily have to be observed by an arbiter, or either player, but it can be. As it can be, why not be consistent, and use this wording in the rule? That was the point I understood Richard to be making.
Stewart Reuben wrote:Ian >The definition of valid in this context seems obvious, but why use the wording 'valid claim'?
I don't really see why it should be necessary to invoke the Bishop. To make an extreme example, if you checkmate your opponent, but don't observe the fact, it is fairly obvious that play will continue. If a flag falls, and nobody observes the fact, isn't it obvious that the same will happen. Why introduce a distinction in the wording that is not especially beneficial? Overall it's not terribly important, but I think it was the point originally being made by Richard.<
If you mean that the word valid could simply be deleted, that is a view. It doesn' really matter. Claim also appears in 10.2. There a person may claim a draw.
I have no idea what you mean by 'invoke the Bishop'.
You are quite wrong to say 'if you checkmate your opponent, but don't observe the fact, it is fairly obvious that play will continue.'
The opponent may notice. The arbiter may notice. In both cases the game will not continue. Moreover, if it should continue, and then attention is drawn to the illegality, while play is still in progress, then the checkmate will stand. It may even stand after the game is finished with a different result.