| # Specifies chess moves as a list in algebraic notation, using PGN conventions | |
| # Force first move to "1. ", then any 1-2 digit number after, relying on model to follow the pattern | |
| root ::= "1. " move " " move "\n" ([1-9] [0-9]? ". " move " " move "\n")+ | |
| move ::= (pawn | nonpawn | castle) [+#]? | |
| # piece type, optional file/rank, optional capture, dest file & rank | |
| nonpawn ::= [NBKQR] [a-h]? [1-8]? "x"? [a-h] [1-8] | |
| # optional file & capture, dest file & rank, optional promotion | |
| pawn ::= ([a-h] "x")? [a-h] [1-8] ("=" [NBKQR])? | |
| castle ::= "O-O" "-O"? | |