In this section we study a class of item-based recommendation
algorithms for producing predictions to users. Unlike
the user-based collaborative ltering algorithm discussed in
Section 2, the item-based approach looks into the set of
items the target user has rated and computes how similar
they are to the target item i and then selects k most
similar items fi1; i2;::: ;ikg. At the same time their cor- responding similarities fsi1; si2;::: ;sikg are also computed.
Once the most similar items are found, the prediction is
then computed by taking a weighted average of the target
user's ratings on these similar items. We describe these two
aspects, namely, the similarity computation and the prediction
generation in details here.