Many companies standardize their metadata by ensuring all records continue to carry an ISBN-10, as well as ISBN-13 and GTIN-13. The laudable goals for this are consistency and to help support sales reps and organizations whose core reports still use ISBN-10. Yes, they should have been updated years ago, but we know that not all of them were.
You many not be aware of it, but your ONIX software may be converting your ISBN-10s to ISBN-13s or vice versa.
Many of these conversions are based on a simple premise: An ISBN-10 can be calculated by removing the first three numbers of an ISBN-13 and calculating the 10th place check digit. An ISBN-10 converts back to ISBN-13 by adding 978 and calculating its check digit. And this all works fine, so long as the ISBN-13 begins with 978.
The problem is that many of these conversions haven't considered ISBN-13s that start with 979.
For example, here's what can happen in a case like this:
- 9790100011006 gets converted to an ISBN-10.
- The resulting ISBN-10 is 0100011004.
- 0100011004, when converted back to ISBN-13, then corresponds to the product associated with 9780100011007.
Does Mother BookNet have to tell you this is very bad indeed? Your primary identifiers are now pointing two ways.
There are currently 34 confirmed, active 979 ISBN-13s from three different distributors in BiblioShare. I'm very pleased to say that none of them carried a converted ISBN-10 in their ONIX feed.* But to illustrate that the problem is real, I checked a very randomly chosen 979 ISBN converted from ISBN-10 to 978 and found it on Amazon. It's in Russian, but it is an active product on Amazon.
The solution is to stop using ISBN-10. People often ask BookNet: "When should I change?" In this case, you're well past the point of "now," so, really and truly, hearts and fingers crossed: You should change now!
We ask that you check to see if you have this problem somewhere in your systems or software. Don't wait until a trading partner reports a problem or until you start to notice lost sales: Check! Now!
*One of those distributors does support a converted ISBN-10 as a "proprietorial" identifier and also uses it for their Record Reference. The only problem I can see here would be in the unlikely case that they carry both the converted ISBN-10-to-978 product as well as the 979 one. Then they would have a duplicated Record Reference (and I assume proprietorial identifier). And I suspect that some part of their processing — or possibly one of their data contacts — requires an ISBN-10. That's a worry.