Also, since the number of promotions to specific pieces is limited, the FEN notation for a game would need to be expanded somehow to keep track of which promotions have already been used.
That is not true, is it? You can see what is on the board, and at all times would be allowed to increase that to what you had in the opening position (which can also assumed to be known). And you cannot promote to an Elephant on the shade where you already have one.
That is not true, is it? You can see what is on the board, and at all times would be allowed to increase that to what you had in the opening position (which can also assumed to be known). And you cannot promote to an Elephant on the shade where you already have one.