Many information sources embody recommender systems as a way of personalizing their content for users [73]. Recommender systems have the effect of guiding
users in a personalized way to interesting or useful objects in a large space of possible options [17]. Recommendation algorithms use input about a customer’s interests
to generate a list of recommended items. At Amazon.com, recommendation algorithms are used to personalize the online store for each customer, for example showing programming titles to a software engineer and baby toys to a new mother [50].