Parameter Black White : Set.(* sets of black (resp. white) squares *)

Parameter BW : Black -> White.(* |Black|<=|White| in full board *)
Axiom BW_One_one : Injective _ _ BW.(* finite board *)
Axiom Finite_Board : Finite Black.(* The Domino one_one map covers White *)
Parameter Domino : White -> Black.Axiom Domino_one_one : Injective _ _ Domino.

(* Specifications: *)
Theorem Domino_covers_Black : Surjective _ _ Domino.