22. The system of claim 21 , wherein the communications of the cluster include structured communications that are each structured using a corresponding markup language, and wherein the instructions to determine the cluster of the communications further include instructions to determine the cluster based on similarity of structural paths of the structured communications of the cluster.
22. The system of claim 21 , wherein the communications of the cluster include structured communications that are each structured using a corresponding markup language, and wherein the instructions to determine the cluster of the communications further include instructions to determine the cluster based on similarity of structural paths of the structured communications of the cluster. 23. The system of claim 22 , wherein the instructions to determine the feature set comprise instructions to: determine structural features of the features based on the structural paths of the structured communications of the cluster, the structural features indicating hierarchical structure of the structural paths.