(** [is_open_feature domain feature_name] returns [true] iff no domain is set or if [feature_name] is defined to be open in the current domain. *)
valis_open_feature:?domain:t->feature_name->bool
(** [is_num domain feature_name] returns [true] iff the domain is set and [feature_name] is defined to be numerical *)
valis_num:?domain:t->feature_name->bool
(** [check_feature ~loc domain feature_name feature_value] fails iff a domain is set and [feature_name,feature_value] is not defined in the current domain. *)