order(tubenose) :-
nostrils(external_tubular),
live(at_sea),
bill(hooked).

order(waterfowl) :-
feet(webbed),
bill(flat).

family(albatross) :-
order(tubenose),
size(large),
wings(long_narrow).

family(swan) :-
order(waterfowl),
neck(long),
color(white),
flight(ponderous).