Another central concept in social network analysis is that of similarity between vertices. In what ways can two actors in a network be similar, and how can we quantify this similarity?
Similarity is relevant in at least two important applications: recommender systems, where the goal is to suggest to a user new products to buy according to what similar users bought or liked, and link prediction, where the task is to predict new connections for a user on social networks according to the connections of similar users.