8. A method comprising: receiving, at a computing device, a metadata request, which comprises a plurality of numeric values retrieved from a media item, as metadata corresponding to the media item; running a first query using the received metadata on first and second metadata sources; responsive to retrieving at least one record from the first query performed in response to the metadata request, transmitting metadata from the retrieved at least one record; and responsive to the metadata request and to extracting no metadata from one of the metadata sources queried in the first query performed in response to the metadata request: forming a second query using additional media identification information as metadata corresponding to the media item, the additional metadata being other than the received metadata; running the second query using the additional metadata, so as to retrieve at least one record from the queried metadata source; and responsive to retrieving at least one record in response to the second query, transmitting metadata from the retrieved at least one record in response to the metadata request; creating, at the computing device, an auxiliary record comprising a mapping between the metadata used in the second query and the metadata used in the first query; and storing the auxiliary record in a linking database that is in communication with the computing device.
8. A method comprising: receiving, at a computing device, a metadata request, which comprises a plurality of numeric values retrieved from a media item, as metadata corresponding to the media item; running a first query using the received metadata on first and second metadata sources; responsive to retrieving at least one record from the first query performed in response to the metadata request, transmitting metadata from the retrieved at least one record; and responsive to the metadata request and to extracting no metadata from one of the metadata sources queried in the first query performed in response to the metadata request: forming a second query using additional media identification information as metadata corresponding to the media item, the additional metadata being other than the received metadata; running the second query using the additional metadata, so as to retrieve at least one record from the queried metadata source; and responsive to retrieving at least one record in response to the second query, transmitting metadata from the retrieved at least one record in response to the metadata request; creating, at the computing device, an auxiliary record comprising a mapping between the metadata used in the second query and the metadata used in the first query; and storing the auxiliary record in a linking database that is in communication with the computing device. 9. The method of claim 8 , wherein the additional media identification information comprises a bar code.