+val any_label : label
+(** Set of all labels which can occur in a tree *)
+
+val new_state : unit -> state
+(** Give a new state (different from all others states) *)
+
+val add_tr : t -> transition -> unit
+(** Add a transition to an asta *)
+
+val add_reco : t -> state -> unit
+(** Add a state to the recognizing states of an asta *)
+
+val add_selec : t -> state -> unit
+(** Add a state to the recognizing states of an asta *)
+
+val add_bot : t -> state -> unit
+(** Add a state to the bottom states of an asta *)
+
+val add_top : t -> state -> unit
+(** Add a state to the top states of an asta *)
+
+val top_states : t -> state list
+(** Give the list of top states of an ASTA *)
+