2-1.5 Availability of data.
Sometimes the reason we cannot determine whether there is
agreement or disagreement in the data values in a field of a record is that there is no value — data
is simply not present. The absence of data makes for uncertainty about matching; this contributes
to the imperfect mapping between field agreement and record matching. When both members of a record
pair have no data value in a particular field, the field cannot contribute to our judgement as to
whether the pair is matched or not. The easiest way to handle this situation is to disallow a blank
field in one record “agreeing” with a blank or anything else in the corresponding
field of another record. A blank in one or both of the fields being compared should make agreement in
our sense indeterminate.
