1. A data processing system for modifying a query during compilation of the query, the query comprising a request for an element of data from a table in a database and parameters identifying the requested element, the data processing system comprising: a computer executing data processing, the computer comprising: query analysis mechanism which determines available information from parameters for locating a classification of the requested element and a classification associated with the query, the requested data classification controlling access to the requested element according to the query associated classification; a request mechanism which prepares a request to an external system, the request asking the external system to provide a suggested action for obtaining a comparison of the requested data classification and the query associated classification, the request comprising the available information; an external system interface which: request a suggested action from an external system to obtain a comparison of the requested data classification and the query associated classification based on the available information, and receives the suggested action from the external system responsive to the sent request; and the computer further comprising: a modification mechanism which incorporates the suggested action into the query to effect comparison of the requested data classification with the query associated classification, wherein based on determining that the external system does not know the requested data classification and the query associated classification, the suggested action comprises a request to call the external system again at execution time of the query for the requested data classification and the query associated classification, and wherein the external system is external to the computer and manages assignment of classifications to users and sections of data in the table.