Depth of Field and Cautious-Greedy Routing in Social Networks

Social networks support efficient decentralized search: people can collectively construct short paths to a specified target in the network. Rank-based friendship—where the probability that person u befriends person v is inversely proportional to the number of people who are closer to u than v is—is an empirically validated model of acquaintanceship that provably results in efficient decentralized search via greedy routing, even in networks with variable population densities. In this paper, we introduce cautious-greedy routing, a variant of greedy that avoids taking large jumps unless they make substantial progress towards the target. Our main result is that cautious-greedy routing finds a path of short expected length from an arbitrary source to a randomly chosen target, independent of the population densities. To quantify the expected length of the path, we define the depth of field of a metric space, a new quantity that intuitively measures the “width” of directions that...

• Type: Conference
• Year: 2007
• Where: ISAAC
• Authors: David Barbella, George Kachergis, David Liben-Nowell, Anna Sallstrom, Ben Sowell
• Keywords: Cautious-greedy Routing finds, Efficient Decentralized Search, ISAAC 2007, Population Densities