Jeff Moss (hacker) Jeff Moss (hacker) Jeff Moss, also known as Dark Tangent, (born January 1, 1975) is an American hacker, computer and internet security expert who founded the Black Hat and DEF CON computer security conferences. Jeff received his first computer at the age of 10. He became fascinated because he wasn't old enough to drive a car or vote, but he could engage in adult conversation with people all over the country. Moss graduated from Gonzaga University with a BA in Criminal Justice. He worked for Ernst & Young, LLP in their Information System Security division and was a director at
Item-item collaborative filtering Earlier collaborative filtering systems based on rating similarity between users (known as user-user collaborative filtering) had several problems: Item-item models resolve these problems in systems that have more users than items. Item-item models use rating distributions "per item", not "per user". With more users than items, each item tends to have more ratings than each user, so an item's average rating usually doesn't change quickly. This leads to more stable rating distributions in the model, so the model doesn't have to be rebuilt as often. When users consume and then rate an item, that item's similar items are picked from