Fascinating ISBNs

After 3 years of successfully overlaying MARC records using a match on field 020 ISBN in Koha I found a file that persistently refused to overlay despite that there was nothing apparently wrong in the raw data. Having an aggressive ISBN and ISSN matching enabled, which allows for these identifiers to be matched regardless of the presence of hyphens in them, or any other typographical symbols, also means that invalid ISBNs and ISSNs are disregarded in the process of matching. Read more