The massive growth of the Internet has made an enormous amount of infor- tion available to us. However, it is becoming very difficult for users to acquire an - plicable one. Therefore, some techniques such as information filtering have been - troduced to address this issue. Recommender systems filter information that is useful to a user from a large amount of information. Many e-commerce sites use rec- mender systems to filter specific information that users want out of an overload of - formation [2]. For example, Amazon. com is a good example of the success of - commender systems [1]. Over the past several years, a considerable amount of research has been conducted on recommendation systems. In general, the usefulness of the recommendation is measured based on its accuracy [3]. Although a high - commendation accuracy can indicate a user's favorite items, there is a fault in that - ly similar items will be recommended. Several studies have reported that users might not be satisfied with a recommendation even though it exhibits high recommendation accuracy [4]. For this reason, we consider that a recommendation having only accuracy is - satisfactory. The serendipity of a recommendation is an important element when c- sidering a user's long-term profits. A recommendation that brings serendipity to users would solve the problem of “user weariness” and would lead to exploitation of users' tastes. The viewpoint of the diversity of the recommendation as well as its accuracy should be required for future recommender systems.

TO PRESUME to multiply books in this day of excellent writers and learned book-makers is a rash thing perhaps for a novice. It may even be a presumption that shall be met by the production itself being driven from the market by the keen, searching criticism of not only the reviewers, but less noted objectors. And yet there are books that meet a ready sale because they seem like "Ishmaelites"--against everybody and everybody against them. Whether this work shall ever accomplish the design of the author may not at all be determined by its sale. While I hope to secure some pecuniary gain that I may accompany it with a companion illustrating what our women have done, yet by no means do I send it forth with the sordid idea of gain. I would rather it would do some good than make a single dollar, and I echo the wish of "Abou Ben Adhem," in that sweet poem of that name, written by Leigh Hunt. The angel was writing at the table, in his vision. The names of those who love the Lord.Abou wanted to know if his was there--and the angel said "No." Said Abou, I pray thee, then, write me as one that loves his fellow-men. That is what I ask to be recorded of me. The angel wrote and vanished. The next night It came again, with a great awakening light. And showed the names whom love of God had blessed. And lo! Ben Adhem's name led all the rest. I desire that the book shall be a help to students, male and female, in the way of information concerning our great names. I have noticed in my long experience as a teacher, that many of my students were wofully ignorant of the work of our great colored men--even ignorant of their names. If they knew their names, it was some indefinable something they had done--just what, they could not tell. If in a slight degree I shall here furnish the data for that class of rising men and women, I shall feel much pleased. Herein will be found many who had severe trials in making their way through schools of different grades. It is a suitable book, it is hoped, to be put into the hands of intelligent, aspiring young people everywhere, that they might see the means and manners of men's elevation, and by this be led to undertake the task of going through high schools and colleges. If the persons herein mentioned could rise to the exalted stations which they have and do now hold, what is there to prevent any young man or woman from achieving greatness? Many, yea, nearly all these came from the loins of slave fathers, and were the babes of women in bondage, and themselves felt the leaden hand of slavery on their own bodies; but whether slaves or not, they suffered with their brethren because of color. That "sum of human villainies" did not crush out the life and manhood of the race. I wish the book to show to the world--to our oppressors and even our friends--that the Negro race is still alive, and must possess more intellectual vigor than any other section of the human family, or else how could they be crushed as slaves in all these years since 1620, and yet to-day stand side by side with the best blood in America, in white institutions, grappling with abstruse problems in Euclid and difficult classics, and master them? Was ever such a thing seen in another people? Whence these lawyers, doctors, authors, editors, divines, lecturers, linguists, scientists, college presidents and such, in one quarter of a century?