19. A method of updating a synonym set stored in a computer readable database to tolerate writing variation in input data when the synonym set is used in checking an input customer data record against a reference data set representing existing information in a computer readable database, wherein the input customer data record contains a data field representing an identifier, and members of the synonym set are first identifier values referring to respective second identifier values, the second identifier values being predetermined identifier values in the reference data set, the method of updating the synonym set when checking the input customer data record against the reference data set comprising the steps of: determining, by a processor, among the predetermined identifier values in the reference data set at least one synonym candidate relating to the value of the data field in the input customer data record using a candidate detection criterion, determining if the value of the data field and a synonym candidate of the at least one synonym candidate fulfill a predetermined synonym acceptance criterion based on at least one quality parameter, wherein said at least one quality parameter takes into account writing variations that are evaluated based on differences in the value of the data field and the synonym candidate, and when the predetermined synonym acceptance criterion is fulfilled, automatically adding the value of the data field to the synonym set in the computer readable database as a member referring to the accepted synonym candidate in the reference data set without intervention of a user and before the synonym set is used in the checking of the input customer data record against the reference data set by searching for a counterpart for the input customer data record from the synonym set.
19. A method of updating a synonym set stored in a computer readable database to tolerate writing variation in input data when the synonym set is used in checking an input customer data record against a reference data set representing existing information in a computer readable database, wherein the input customer data record contains a data field representing an identifier, and members of the synonym set are first identifier values referring to respective second identifier values, the second identifier values being predetermined identifier values in the reference data set, the method of updating the synonym set when checking the input customer data record against the reference data set comprising the steps of: determining, by a processor, among the predetermined identifier values in the reference data set at least one synonym candidate relating to the value of the data field in the input customer data record using a candidate detection criterion, determining if the value of the data field and a synonym candidate of the at least one synonym candidate fulfill a predetermined synonym acceptance criterion based on at least one quality parameter, wherein said at least one quality parameter takes into account writing variations that are evaluated based on differences in the value of the data field and the synonym candidate, and when the predetermined synonym acceptance criterion is fulfilled, automatically adding the value of the data field to the synonym set in the computer readable database as a member referring to the accepted synonym candidate in the reference data set without intervention of a user and before the synonym set is used in the checking of the input customer data record against the reference data set by searching for a counterpart for the input customer data record from the synonym set. 20. A method as defined in claim 19 , wherein the synonym set is empty before adding the value of the data field to the synonym set.