1. A method of generating a characterizing summary in a preservation system, the method comprising: collecting first information about content data or one or more metadata included in a preservation object constructed for the content data; collecting second information about the content data and the metadata by searching for other preservation objects or other metadata; generating a characterizing summary for the content data or the metadata according to the first information and the second information; and adding the characterizing summary to the preservation object, wherein the preservation object is stored on one or more storage media in the preservation system.