1. A method of processing a data record for finding a counterpart in a reference data set, the method comprising the steps of: determining in the data record a value of a data field, the data field representing an identifier, determining from a set of predetermined identifier values at least one synonym candidate for the value of the data field, determining if a synonym candidate and the value of the data field fulfill a predetermined synonym acceptance criterion taking into account writing variations, and if the predetermined synonym acceptance criterion is fulfilled, associating the value of the data field and the synonym candidate as synonyms, and searching for a counterpart for the data record by comparing to entries of the reference data set the value of the data field and/or a synonym associated with the value of the data field after determining if the predetermined synonym acceptance criterion is fulfilled.