17. The computer readable medium of claim 16 , wherein the instructions cause the one or more data processing apparatus to perform operations further comprising: representing the reference image and co-selected images as nodes in a weighted graph, each node being connected to other nodes by weighted edges representing sequential selections of the images represented by the node and the other nodes; and wherein the measure of relevance for each co-selected image is generated based on the weighted edges.
17. The computer readable medium of claim 16 , wherein the instructions cause the one or more data processing apparatus to perform operations further comprising: representing the reference image and co-selected images as nodes in a weighted graph, each node being connected to other nodes by weighted edges representing sequential selections of the images represented by the node and the other nodes; and wherein the measure of relevance for each co-selected image is generated based on the weighted edges. 18. The computer readable medium of claim 17 , wherein a weighted edge connecting a pair of nodes has a weight that is indicative of a number of sequential selections of images represented by the pair of nodes.