Module Type SUBST_SOUND.
Declare Module VSD: VERISTAR_DEFS.

Axiom subst_pure_sound: forall i e a,
pure_atom_denote (subst_pure i e a) =
match a with Eqv e1 e2 => pure_atom_denote (Eqv (subst_expr i e e1) (subst_expr i e e2))
end.