Question: What information is contained in the social graph of tweet authors?
Answer:  the graph, composed of three types of nodes: tweets (T), users (U) and the “world” (W). Edges are created between nodes and weighted as follows: T-T the unigram cosine similarity between tweets, T-U weighted 100 between a tweet and its author, U-U weighted 1 between two users in a “follows” relationship and U-W weighted 0.001 to ensure a connected graph for the mad algorithm.