1. A method for generating concept structures from signature reduced clusters (SRCs), comprising: retrieving from a storage at least one SRC including a cluster of signatures respective of a plurality of multimedia data elements (MMDEs); generating metadata for the cluster of signatures included in the at least one retrieved SRC; associating the generated metadata with the at least one retrieved SRC; reducing a number of signatures in the at least one retrieved SRC to include only signatures that uniquely identify the at least one retrieved SRC by temporarily removing a signature from the at least one retrieved SRC, checking if MMDEs associated with the at least one retrieved SRC can be recognized without the removed signature, and permanently removing the signature from the at least one retrieved SRC, if the MMDEs associated with the SRC can be recognized; and matching the at least one retrieved SRC with a plurality of previously generated SRCs stored in the storage, wherein each of the plurality of previously generated SRCs that matches the at least one retrieved SRC forms a concept structure, wherein the concept structure includes at least metadata associated with the SRC matching the at least one retrieved SRC.