()
(mammal isa animal)
(mammal has vertebra)
(cat isa mammal)
(cat has fur)
(bear isa mammal)
(bear has fur)
(fish isa animal)
(fish lives-in water)
(whale isa mammal)
(whale lives-in water)
(animal isa physical-object)
(physical-object has mass)
(cat isa pet)
(pet has owner)
(cat weight 12)
(whale weight 66000)
(bear weight 240)