1. In a data processing system, a method for mapping data fields from a source data set to a destination data set, in the method comprising: defining a set of rules comprising a plurality of field types, wherein each field type is associated with one or more string or substring expressions specifying a field name; ordering said rules according to how likely a given rule will correctly identify a field; receiving a source data set comprising a plurality of data fields; mapping data fields of the source data set to data fields of the destination data set by determining a field type for each source data field, based on application of the rules; and synchronizing the source data set with the destination data set, so that values from data fields of the source data set are synchronized with field values from corresponding data fields of the destination data set.