def getRecord(metadataPrefix, identifier):
    """Get a record for a metadataPrefix and identifier.

        metadataPrefix - identifies metadata set to retrieve
        identifier - repository-unique identifier of record
        
        Should raise error.CannotDisseminateFormatError if
        metadataPrefix is unknown or not supported by identifier.
        
        Should raise error.IdDoesNotExistError if identifier is
        unknown or illegal.

        Returns a header, metadata, about tuple describing the record.
        """
