Definition inPhantom := Phantom Prop.Definition onPhantom T P (x : T) := Phantom Prop (P x).Definition bijective_in aT rT (d : mem_pred aT) (f : aT -> rT) :=
  exists2 g, prop_in1 d (inPhantom (cancel f g))
           & prop_on1 d (Phantom _ (cancel g)) (onPhantom (cancel g) f).Definition bijective_on aT rT (cd : mem_pred rT) (f : aT -> rT) :=
  exists2 g, prop_on1 cd (Phantom _ (cancel f)) (onPhantom (cancel f) g)
           & prop_in1 cd (inPhantom (cancel g f)).

(* Specifications: *)
Lemma sub_in1 (Ph : ph {all1 P1}) : prop_in1 d1' Ph -> prop_in1 d1 Ph.
Lemma sub_in11 (Ph : ph {all2 P2}) : prop_in11 d1' d2' Ph -> prop_in11 d1 d2 Ph.
Lemma sub_in111 (Ph : ph {all3 P3}) : prop_in111 d1' d2' d3' Ph -> prop_in111 d1 d2 d3 Ph.
Lemma subon1 (Phf : ph (allQ1 f)) (Ph : ph (allQ1 f)) : prop_on1 d2' Phf Ph -> prop_on1 d2 Phf Ph.
Lemma subon1l (Phf : ph (allQ1l f)) (Ph : ph (allQ1l f h)) : prop_on1 d2' Phf Ph -> prop_on1 d2 Phf Ph.
Lemma subon2 (Phf : ph (allQ2 f)) (Ph : ph (allQ2 f)) : prop_on2 d2' Phf Ph -> prop_on2 d2 Phf Ph.
Lemma sub_in2 T d d' (P : T -> T -> Prop) : sub_mem d d' -> forall Ph : ph {all2 P}, prop_in2 d' Ph -> prop_in2 d Ph.
Lemma sub_in3 T d d' (P : T -> T -> T -> Prop) : sub_mem d d' -> forall Ph : ph {all3 P}, prop_in3 d' Ph -> prop_in3 d Ph.
Lemma sub_in12 T1 T d1 d1' d d' (P : T1 -> T -> T -> Prop) : sub_mem d1 d1' -> sub_mem d d' -> forall Ph : ph {all3 P}, prop_in12 d1' d' Ph -> prop_in12 d1 d Ph.
Lemma sub_in21 T T3 d d' d3 d3' (P : T -> T -> T3 -> Prop) : sub_mem d d' -> sub_mem d3 d3' -> forall Ph : ph {all3 P}, prop_in21 d' d3' Ph -> prop_in21 d d3 Ph.