Definition compatible m1 m2 := forall k v1 v2, m1 k = Some v1 -> m2 k = Some v2 -> v1 = v2.Global Instance compatible_refl : Reflexive compatible.Global Instance compatible_comm : Symmetric compatible.

Lemma map_incl_compatible : forall m1 m2 m3 (Hincl1 : map_incl m1 m3) (Hincl2 : map_incl m2 m3), compatible m1 m2.