Chess Invariants
Summary
An in-depth look at modeling chess as a concurrent system, focusing on invariants and how they split into state invariants and transition invariants. It walks through examples such as TurnParity and PreviousPlayerNotInCheck, and explains how basic chess rules constrain state changes. The post also notes how extending the model (castling, en passant, pawn promotion) can affect invariant properties, illustrating the trade-offs of formal reasoning in system design.