1. A method of analyzing documents belonging to a corpus, the method comprising: computing a composite hash value for a current document from the corpus; determining whether a previous document having the same composite hash value as the current document has been analyzed; in the event that a previous document having the same composite hash value as the current document has not been analyzed, analyzing the current document, wherein analyzing the current document includes determining one or more items of analytic metadata to be associated with the current document; in the event that a previous document having the same composite hash value as the current document has been analyzed, associating the current document with one or more items of analytic metadata determined from analyzing the previous document; and storing a representation of the association between the one or more items of analytic metadata and the current document.