(* File: NSound.v  (last edited on 27/10/2000) (c) Klaus Weich  *)
Require Export Le_Ks.
Require Export Derivable_Tools.
Definition nsound (work : nf_list) (ds : disjs) (ni : nested_imps)
(ai : atomic_imps) (a : atoms) (context : flist) :=
forall c : normal_form,
in_ngamma work ds ni ai a c -> Derivable context (nf2form c).

Lemma nsound_eqv :
forall (work : nf_list) (ds : disjs) (ni1 ni2 : nested_imps)
(ai : atomic_imps) (a : atoms) (context : flist),
eqv_ni ni1 ni2 ->
nsound work ds ni1 ai a context -> nsound work ds ni2 ai a context.