It's suggested to extend the Instance schema of Inventory storage with a unique, optional property matchKey.
Instance.matchKey can be used in a setting where multiple libraries contribute bibliographic records to the same FOLIO Inventory – a shared index – and thus need a way to identify identical instances across multiple catalogs in order to provide updates to bibliographic data or holdings in the shared index. One option is to use match key values based on metadata in the bibliographic record for example.
Example match key
MARC records are matched in the system via an algorithm which includes portions of the title, author, publisher, imprint date and a few other elements. The system does not use ISBNs, ISSNs or OCLC numbers since many records do not contain these elements (particularly older records or non-monographs).
ReShare Shared Inventory allows a group of libraries to contribute each member’s bibliographic and holdings metadata to a central repository. The ReShare software matches and deduplicates records and creates master records that are associated with the holdings for each contributing library.
Please note that the change includes a new unique index added to the DB schema.