Задача о птицах, наследование. 506 Type Error: The functor does not belong to the domain

DOMAINS
Object=symbol
Prop=travel(symbol);color(symbol);sound(symbol);size(symbol)
list_of_properties=Prop*
name=name(Object)
isa=isa(Object)
PREDICATES
frame(name,isa,list_of_properties,list_of_properties)
get(Prop,Object)
nondeterm member(prop,list_of_properties)
CLAUSES
member(X,[X|_]).
member(X,[_|T]):-member(X,T).
frame(name(bird),isa(animal),[travel(flies)],[]).
frame(name(ostrich),isa(bird),[travel(walk)],[]).
frame(name(penguin),isa(bird),[color(brown)],[travel(walks)]).
frame(name(opus),isa(penguin),[],[]).
frame(name(robin),isa(bird),[color(red)],[sound(sing)]).
frame(name(canary),isa(bird),[color(yellow),sound(sing)],[size(small)]).
frame(name(tweety),isa(canary),[],[color(white)]).
get(Prop,Object):-frame(name(Object),_,list_of_properties,_),member(Prop,list_of_properties).
get(Prop,Object):-frame(name(Object),_,_,list_of_properties),member(Prop,list_of_properties).
get(Prop,Object):-frame(name(Object),isa(Parent),_,_),get(Prop,Parent).
GOAL
get(color(white),object).

get(Prop,Object):-frame(name(Object),_,List_of_properties,_),member(Prop,List_of_properties).
get(Prop,Object):-frame(name(Object),_,_,List_of_properties),member(Prop,List_of_properties).

get(color(white),Obj).