41. The method of claim 3 in which each vector represents a corresponding user in a community, and each feature of each vector represents a preference of the corresponding user towards an object in a set of objects.
41. The method of claim 3 in which each vector represents a corresponding user in a community, and each feature of each vector represents a preference of the corresponding user towards an object in a set of objects. 42. The method of claim 41 , further comprising recommending an object to a user corresponding to the vector x based on the vector y.