Introduction to recommender engines

In today's digital world, recommendation engines are ubiquitous among many industries. Many online businesses, such as streaming, shopping, news, and social media, rely at their core on recommending the most relevant articles, news, and items to their users. How often have you clicked on a suggested video on YouTube, scrolled through your Facebook feed, listened to a personalized playlist on Spotify, or clicked on a recommended article on Amazon?

If you ask yourself what the term relevant means for the different services and industries, you are on the right track. In order to recommend relevant information to the user, we need to first define a relevancy metric, and a way to describe and compare different items and their similarity. These two properties are the key to understanding the different recommendation engines. We will learn more about this in the following sections of this chapter.

While the purpose of a recommendation engine...