28. The multimedia device of claim 26 , wherein the data structure update unit only updates changed portions of the data structure.
26. A multimedia device to automatically and efficiently classify content stored therein, comprising: a storage unit located on a processor to store a plurality of digital content; a data structure generation unit located on the processor to generate a data structure having a plurality of nodes, based on the content stored in the storage unit; an extraction unit located on the processor to extract a descriptor of the new digital content to be stored in the storage unit; a cluster classification unit located on the processor to classify the new digital content and the plurality of digital content using a clustering scheme and the extracted descriptor; and a data structure update unit located on the processor to update the data structure based on the classification.