Koha How-To

Match Points versus Match Checks in Koha

Some of you may have played around with the record matching rules in Koha. (Administration->Record Matching Rules) These Record Matching rules are used when importing new batches of MARC records into your catalog. Lately, I’ve been asked to explain the difference between a ‘Match Point’ and a ‘Match Check’ in the matching rule set up. Others have written about the Import Rules here -> /2012/10/22/basic-overview-of-match-points/

First, to review Match Points. Match Points are the criteria that you enter that must be met in order for an incoming record to match an existing MARC record in your catalog. You can have multiple match points on an import rule each with its own score. An incoming record will be compared against your existing records (‘one record at a time’) and given a score for each match point. When the total score of the matchpoints matches or exceeds the threshold given for the matching rule, Koha assumes a good match and imports/overlays according your specifications in the import process. An area to watch out for here is the sum of the match points. Doublecheck that the matches you want will add up to a successful match.

Example:
Threshold of 1000
Match Point on 020$a 1000
Match Point on 022$a 1000
Match Point on 245$a 500
Match Point on 100$a 100

In the example above, a match on either the 020$a or the 022$a will result in a successful match. A match on 245$a title and 100$a author (and not on 020$a or 022$a) will only add up to 600 and not be a match. And a match on 020$a and 245$a will result in 1500 and while this is a successful match, the extra 500 point for the 245$a title match are superfluous. The incoming record successfully matched on the 020$a without the need for the 245$a match. However, if you assigned a score of 500 to the 100$a Match Point, a match on 245$a title and 100$a author will be considered a successful match (total of 1000) even if the 020$a is not a match.

Now for Match Checks….
Match Checks are not commonly used in import rules. However, they can serve a couple of purposes in matching records. First, match checks can be used as the matching criteria instead of the match points if your indexes are stale and out of date. The match checks go right for the data instead of relying on the data in the indexes. (If you fear your indexes are out of date, a rebuild of your indexes would be a great idea and solve that situation!) The other use for a Match Check is as a “double check” or “veto” of your matching rule. For example, if you have a matching rule as below:

Threshold of 1000
Match Point on 020$a 1000
Match Check on 245$a

Koha will first look at the 020$a tag/subfield to see if the incoming record matches an existing record. If it does, it will then move on to the Match Check and look directly at the 245$a value in the incoming data and compare it to the 245$a in the existing ‘matched’ record in your catalog. If the 245$a matches, Koha continues on as if a match was successful. If the 245$a does not match, then Koha concludes that the two records are not a match after all. The Match Checks can be a really useful tool in confirming true matches.

Match Points and Match Checks are powerful tools in the import process. Harness the power of these two matching criteria and make your data behave for you!