Definition identify := mk (M.set a b uf.(m)) identify_wf.

(* Specifications: *)
Lemma repr_identify_1: forall x, repr uf x <> a -> repr identify x = repr uf x.
Lemma repr_identify_2: forall x, repr uf x = a -> repr identify x = repr uf b.
Lemma repr_identify_1: forall x, repr uf x <> a -> repr identify x = repr uf x.
Lemma repr_identify_2: forall x, repr uf x = a -> repr identify x = repr uf b.