1-3.4 Data propagation rules.
There is another important kind of transformation. These
are the so called data propagation rules. These algorithms produce
virtual data -- field values that
were not actually in the original record. The calculation of a birth date from an age at an event is
a simple example of such a rule. In some resources certain data is sometimes present, in others
never. Propagation may provide data to be compared against where it was not present or only
indirectly surmised. In comparing records the record linkage system does not weight agreement of
virtual data as heavily as agreement of real data.
