1 walking dog
  1.1 get dog ready
    1.1.1 get leash
  1.2 get yourself ready
    1.1.1 put on shoes
      1.1.1.1 tie shoes
  1.3 take dog outside
    1.1.1 open door
      1.1.1.1 close door
      1.1.1.2 lock door
        1.1.1.1.1 put key in door