12. The system of claim 10 , wherein a respective document is determined to be related to one or more other documents in the respective cluster based on a resource locator of the respective document and resource locators of the one or more other documents in the respective cluster.
13. The system of claim 12 , wherein: a plurality of documents in the set of documents each have a resource locator; the instructions for grouping the set of documents into a plurality of clusters include instructions for: ordering the set of documents in accordance with the resource locators; and selecting a respective plurality of consecutive documents from the ordering for inclusion in the respective cluster.