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Yes, George has seen it right. I do want programmer accuracy, for exactly the purpose he describes: allowing defenition of complete Chess variants. I imagine multi-variant engines such as Fairy-Max, Nebiyu and Sjaak to allow the use of Betza notation in their configuration files for defining the variants they play (where now they use (often very cumbersome) custom notations). And in any case I would want those engines to send the description of the variant to the GUI, so that the latter becomes fully rule-aware, and can do tasks like legality checking, highlighting possible move targets of a picked-up piece, indicating victims of a capture you hover over, convert moves to and from Standard Algebraic Notation, detect check and checkmate, etc. So that all that people would need to do is add the Betza-style definition of the variant plus the initial setup in a configuration file to have a full-fledged program to play it.