9. The method of claim 8 , further comprising: constructing a set of connections between the first set of nodes and the second set of nodes; wherein each connection in the set of connections connects a node in the first set of nodes and a node in the second set of nodes if there is an association between the linguistic word represented by the node in the first set of nodes and the visual word represented by the node in the second set of nodes; wherein each connection in the set of connections comprises a first directed edge and a second directed edge; wherein the first directed edge is directed from the node in the first set of nodes to the node in the second set of nodes; wherein the second directed edge is directed from the node in the second set of nodes to the node in the first set of nodes; wherein the first directed edge is labeled with a first probability; wherein the first probability indicates a probability that the visual word represented by the node in the second set of nodes occurs in an image in the set of images described by the linguistic word represented by the node in the first set of nodes; wherein the second directed edge is labeled with a second probability; wherein the second probability indicates a probability that the linguistic word represented by the node in the first set of nodes describes an image in the set of images in which the visual word represented by the node in the second set of nodes occurs; wherein the random walk through the bipartite graph is performed based on probabilities labeled on directed edges in connections between nodes in the first set of nodes and nodes in the second set of nodes; and wherein the random walk, with restart from the first node, through the bipartite graph is performed based on probabilities labeled on directed edges in connections between nodes in the first set of nodes and nodes in the second set of nodes, with restarts at the first node based on a restart probability.
8. The method of claim 7 wherein the step of deriving the association score between the first node and the second node includes: generating a first set of scores based on a random walk through the bipartite graph; generating a second set of scores based on a random walk, with restart from the first node, through the bipartite graph; and deriving the association score based on the first set of scores and the second set of scores.