“…Kapoor et al [11] point out in their pioneering work that an item can be novel in three ways: (1) it is new to the system and thus for every user (cold-start), (2) it is known to the system but new to the single user, (3) it is known to the user long before but forgotten at the moment. Unfortunately, existing studies [1], [2], [3], [4], [5], [6], [7], [8] focus on novel recommendation tasks under the above definition (2) (3), and none of them has ever taken cold-start items into consideration. Meanwhile, previous research on cold-start recommendation [12], [13], [14], [15], [16], [17], [18] does not include long-tail items, either.…”