Inductive compond_relation {A: Type} (R1 R2: relation A) : relation A :=
  | compond_intro: forall x y z, R1 x y -> R2 y z -> compond_relation R1 R2 x z.Inductive compond_relation {A: Type} (R1 R2: relation A) : relation A :=
  | compond_intro: forall x y z, R1 x y -> R2 y z -> compond_relation R1 R2 x z.

Lemma compond_relation_spec: forall {A} (R1 R2: relation A) x z, compond_relation R1 R2 x z -> exists y, R1 x y /\ R2 y z.