(Dbf_sql.SQL_db.column * Dbf_sql.SQL_db.column -> 'a) ->
Dbf_sql.SQL_db.table list * Dbf_sql.SQL_db.table list ->
object
val glade : Dbf_gladeWidgets.constraint_window
val view1 : Dbf_virtualTableGUI.DW.db_widget
val view2 : Dbf_virtualTableGUI.DW.db_widget
method private _cb__cancel_button_clicked : unit -> unit
method private _cb__ok_button_clicked : unit -> unit
method private _grab_input : Dbf_sql.SQL_db.column * Dbf_sql.SQL_db.column
method start : unit -> unit
end