如何在Prolog中返回推荐列表？

rating(john, item1, 4).
rating(john, item2, 3).
rating(john, item3, 5).
rating(lisa, item1, 5).
rating(lisa, item2, 4).
rating(lisa, item3, 2).

similarity(User1, User2, Similarity) :-
    findall(R1, rating(User1, _, R1), Ratings1),
    findall(R2, rating(User2, _, R2), Ratings2),
    average(Ratings1, Avg1),
    average(Ratings2, Avg2),
    deviations(Ratings1, Avg1, Deviations1),
    deviations(Ratings2, Avg2, Deviations2),
    covariance(Deviations1, Deviations2, Cov),
    variance(Deviations1, Var1),
    variance(Deviations2, Var2),
    Similarity is Cov / (sqrt(Var1) * sqrt(Var2)).

recommendations(User, Recommendations) :-
    findall(Item, rating(_, Item, _), AllItems),
    findall(Sim-Item, (rating(OtherUser, Item, _), similarity(User, OtherUser, Sim)), Similarities),
    sort(Similarities, SortedSimilarities),
    reverse(SortedSimilarities, ReverseSortedSimilarities),
    findall(Item, (member(_-Item, ReverseSortedSimilarities), \+ rating(User, Item, _)), Recommendations).

?- recommendations(john, Recommendations).