Canonical Structure union_form s1 s2 h1 h2 :=
Form (@union_pf s1 s2 h1 h2).

Lemma foundy_pf x y (s : Search.form x) : axiom x y (foundy_tag (y :: s)).
Canonical Structure foundy_form x y (s : Search.form x) :=
Form (foundy_pf y s).