Table 1: An example of a user-item matrix.
(a)

Alice: (like) Shrek, Snow White, (dislike) Superman
Bob: (like) Snow White, Superman, (dislike) spiderman
Chris: (like) spiderman, (dislike) Snow white
Tony: (like) Shrek, (dislike) Spiderman

(b)

ShrekSnow WhiteSpider-manSuper-man

AliceLikeLikeDislike
BobLikeDislikeLike
ChrisDislikeLike
TonyLikeDislike?