8. A system, comprising: a processor; a concept hierarchy module executable by the processor to: determine a concept hierarchy corresponding to a document corpus; and automatically update the concept hierarchy responsive to detecting that a new document is added to the document corpus, wherein the new document is without user intervention added to the document corpus and a deleted documents is without user intervention removed from the document corpus by an monitoring agent; and an interface module executable by the processor to: generate an interface based on the concept hierarchy; transmit the interface for display to a display device; receive user input at the interface; update the interface to reflect results of performing a navigation operation on the concept hierarchy based on the user input; update the interface to reflect results of performing a search operation on the concept hierarchy based on the user input; and update the interface to reflect results of performing a modification operation on the concept hierarchy based on the user input.
11. The system of claim 8 , wherein adding a document to the document corpus results in removing of a concept from the concept hierarchy.