Recommender systems apply knowledge discovery techniques
to the problem of making personalized recommendations for
information, products or services during a live interaction.
These systems, especially the k-nearest neighbor collabora-
tive ltering based ones, are achieving widespread success on
the Web. The tremendous growth in the amount of avail-
able information and the number of visitors to Web sites in
recent years poses some key challenges for recommender sys-
tems. These are: producing high quality recommendations,
performing many recommendations per second for millions
of users and items and achieving high coverage in the face of
data sparsity. In traditional collaborative ltering systems
the amount of work increases with the number of partici-
pants in the system. New recommender system technologies
are needed that can quickly produce high quality recom-
mendations, even for very large-scale problems. To address
these issues we have explored item-based collaborative l-
tering techniques. Item-based techniques rst analyze the
user-item matrix to identify relationships between dierent
items, and then use these relationships to indirectly compute
recommendations for users.
In this paper we analyze dierent item-based recommen-
dation generation algorithms. We look into dierent tech-
niques for computing item-item similarities (e.g., item-item
correlation vs. cosine similarities between item vectors) and
dierent techniques for obtaining recommendations from them
(e.g., weighted sum vs. regression model). Finally, we ex-
perimentally evaluate our results and compare them to the
basic k-nearest neighbor approach. Our experiments sug-
gest that item-based algorithms provide dramatically better
performance than user-based algorithms, while at the same
time providing better quality than the best available user-
based algorithms.