Proof fun X A a Y B b b' H1 H2 E e => e b' H1 H2.
(** Direct elements of a pointed graph (X, A, a) are simply the pointed graphs of the form (X, A, a') such that (A a' a), that is, the pointed graphs we obtain by shifting the root one edge downwards: *)

(* Specifications: *)
Lemma ELT_direct :
forall (X : Typ1) (A : Rel X) (a a' : X), A a' a -> ELT X A a' X A a.