The index is an inverted index on the match-keys generated by each input reference as it is processed. As each reference is read into the system, the attribute values are input into a match-key generator. The resulting match-key is then used to lookup all other previously processed references that also generated that same match key. The previously processed references that have the same match-key then become the candidates to test against the input records by the match rules. It is important to note that these are the ONLY candidates to be tested for matching. After the input record has been matched to all of the candidate records, the input record is also inserted into the index (lookup table). Figure 22 shows the first step where the match-key is generated and used to lookup matching candidates.

The same process show in Figure 22 is also shown in Figure 23using the match-key generator of Example 1. Note that in Figure 23, the input reference "PHILIP DOE" generates the match-key "PDOE" that returns three matching candidates. Which of these three actually match the input reference will depend on the rules. If the rules require that first and last names must be exact, then only the candidate reference R8 would be a match. On the other hand, if the rules allow the first name to match by their Soundex values, then both candidate references R4 and R8 would be a match.

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