Privacy-preserving collaborative filtering

A non-transitory computer-readable storage medium storing instructions that when executed by a computer cause the computer to perform a method, the method comprising:

• receiving a user-ratings snapshot, wherein the user-ratings snapshot comprises a first group identifier for a first end-user and a first ratings vector for the first end-user, and wherein the ratings vector indicates a rating value for each of a plurality of rated items;
• associating the first ratings vector to a ratings group identified by the first group identifier;
• receiving a recommendation request indicating a second group identifier for a second end-user, wherein the second group identifier identifies the ratings group;
• determining a plurality of ratings vectors associated with the ratings group;
• and
• generating a recommendation based on the plurality of ratings vectors, wherein generating the recommendation involves:
• determining, from the plurality of ratings vectors, a corresponding plurality of standardized ratings for a rated item of one or more rated items, wherein a standardized rating from a respective end-user is standardized based on a rating average for the respective end-user;
• computing a standardized average rating for the rated item by computing the average for the plurality of standardized ratings;
• computing an average rating for the rated item by adding the second end-user's average rating to the standardized average rating;
• and
• selecting an item that has the highest average rating among the one or more rated items.

An apparatus comprising:

• a processor;
• a memory;
• a communication module to receive a user-ratings snapshot, wherein the user-ratings snapshot comprises a first group identifier for a first end-user and a first ratings vector for the first end-user, and wherein the ratings vector indicates a rating value for each of a plurality of rated items;
• a group-identifying module to associate the first ratings vector to a ratings group identified by the first group identifier;
• and
• a recommendation module to generate a recommendation based on the ratings group,
• wherein the communication module is further configured to receive a recommendation request indicating a second group identifier for a second end-user, wherein the second group identifier identifies the ratings group, and
• wherein the recommendation module is further configured to:
• determine a plurality of ratings vectors associated with the ratings group;
• and
• generate a recommendation based on the plurality of ratings vectors, and
• wherein while generating the recommendation, the recommendation module is further configured to:
• determine, from the plurality of ratings vectors, a corresponding plurality of standardized ratings for a rated item of one or more rated items, wherein a standardized rating from a respective end-user is standardized based on a rating average for the respective end-user;
• compute a standardized average rating for the rated item by computing the average for the plurality of standardized ratings;
• compute an average rating for the rated item by adding the second end-user's average rating to the standardized average rating;
• and
• select an item that has the highest average rating among the one or more rated items.