Hello, I am currently writing my Bachelor thesis and am using Mahout for a recommendation system. I bought the book Mahout in Action and understand how the similarity matrix works for the distributed RecommenderJob. However, this explanation only shows how it works when the user has expressed some preferences towards the items. I would like to know how this works when there are no preferences (booleanData true). Are all preference values somehow inferred? Or treated as 1? I would also like to know what role the similarity metrics play in these Map/Reduce implementation.
Thank you very much in advance, William
