Security hacker laws against computer hacking. Neal Patrick testified before the U.S. House of Representatives on September 26, 1983, about the dangers of computer hacking, and six bills concerning computer crime were introduced in the House that year. As a result of these laws against computer criminality, white hat, grey hat and black hat hackers try to distinguish themselves from each other, depending on the legality of their activities. These moral conflicts are expressed in The Mentor's "The Hacker Manifesto", published 1986 in "Phrack". Use of the term hacker meaning computer criminal was also advanced by the title "Stalking the Wily Hacker",
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