Definition list_bound {A: Type} (f: A -> Prop) (l: list A):=
  Forall f l /\  NoDup l.Definition vset := Ensemble var.Definition expr_bound (n: vset) (e: expr) :=
 match e with Nil => True | Var v => n v end.Definition pure_bound (n: vset) (a : pure_atom) :=
 match a with
 | Eqv e e' => expr_bound n e /\ expr_bound n e'
 end.Definition space_bound (n: vset) (a: space_atom) :=
 match a with
 | Next e e' =>  expr_bound n e /\ expr_bound n e'
 | Lseg e e' =>  expr_bound n e /\ expr_bound n e'
 end.Definition pures_bound n := list_bound (pure_bound n).Definition spaces_bound n := list_bound (space_bound n).Definition pures_bound' n := Forall (pure_bound n).Definition spaces_bound' n := Forall (space_bound n).Definition clause_bound' (n: vset)  (cl: clause) :=
 match cl with
 | PureClause pi pi' _ _ =>  pures_bound' n pi /\ pures_bound' n pi'
 | PosSpaceClause pi pi' sigma =>
    pures_bound' n pi /\ pures_bound' n pi'/\ spaces_bound' n sigma
 | NegSpaceClause pi sigma pi' =>
    pures_bound' n pi /\ pures_bound' n pi'/\ spaces_bound' n sigma
 end.Definition clause_bound (n: vset)  (cl: clause) :=
 match cl with
 | PureClause pi pi' _ _ =>  pures_bound n pi /\ pures_bound n pi'
 | PosSpaceClause pi pi' sigma =>
    pures_bound n pi /\ pures_bound n pi'/\ spaces_bound n sigma
 | NegSpaceClause pi sigma pi' =>
    pures_bound n pi /\ pures_bound n pi'/\ spaces_bound n sigma
 end.

Lemma pure_bound_more: forall n n' a, Included _ n n' -> pure_bound n a -> pure_bound n' a.