SALSA and PageRank are algorithms that analyze the link structure of web pages to determine authoritative pages. SALSA models the web as two interacting Markov chains, with one chain representing hubs (pages that link to many others) and the other representing authorities (pages that many point to). The principal community identified by SALSA consists of pages frequently visited in these random walks. PageRank also models the web as a graph and web surfing as a random walk. It defines a page's rank based on the ranks of pages that link to it, so pages linked from many highly ranked pages receive higher scores. Both use random walk-based models to determine important pages based on link structure.