OCLC Numbers will be going from maximum 9 digits to 10 digits in about a year, July 2013.
I’m pretty confident my software is all able to handle OCLC numbers of 10 or more digits just fine; there’s another change that some of my software will have to be updated to accomodate: A new “prefix” for OCLC numbers,
"on"+10 or more digits.
That’s added to existing prefixes “ocm” for 8 digit OCLC numbers (with some right and left padding ordinarily in marc records), and “ocn” for 9 digit OCLC numbers.
They document the new “ocn” as “10 or more digits”, so hopefully this means they’ll never have to introduce yet another prefix, even if they eventually go to 11.
It’s not entirely clear to me what parts of the MARC record you should expect to see these ocm/ocn/on prefixes, vs the “(OCoLC)” prefix, vs no prefix at all. But I think they all show up all over the place in front of OCLC numbers, even places they aren’t “supposed” to be. I do have various code that needs to recognize these prefixes to a) remove them to get the actual OCLC number for matching with external databases, b) Use the prefix as a clue it really is an OCLC number. I’ll have to look through my code for places it’s doing this with “ocn” and “ocm” (fortunately pretty greppable strings, unlikely to appear except in this context), and add “on” to the recognition algorithms.
Thanks to OCLC for the year notice. Over a year notice of a change is great! Now if they can just figure out how to give _any_ advance notice with an actual date for Web Service changes, like they do for MARC changes! If you see the Web Services as your future, time to start treating them at least almost as seriously as you treat your non-web-service MARC issues.