(defparameter *facts*
  '((day-boat isa boat)
    (day-boat nav-zone 5)
    (wheel-boat isa boat)
    (wheel-boat nav-zone 100)
    (engineless-boat isa day-boat)
    (small-multi-hull-boat isa day-boat)
    (pedal-wheel-boat isa engineless-boat)
    (pedal-wheel-boat isa wheel-boat)
    (small-catamaran isa small-multi-hull-boat)
    (pedalo isa pedal-wheel-boat)
    (pedalo isa small-catamaran)
    ))