crust(thin).
crust(handtossed).
crust(deepdish).
cheese(mozzarella).
cheese(cheddar).
cheese(parmesan).
topping(none).
topping(pepperoni).
topping(sausage).
topping(onion).
topping(pepper).
likes(author, (thin, handtossed), (cheddar, parmesan), (sausage, onion)).