There are many different kinds of "identifiers" such as ISBN, ISSN, LCCN, OCLC #, etc, etc - see also 01X-09X - Numbers and Codes-General Information
In FOLIO each of the above has both an identifier type (the above) and a value (the identifier itself).
The following list of identifier types have been added to the identifierTypes db table via API with /opt/folio/api/POST/identifier-types.pl:
- GPO Item Number
- ISBN
- ISSN
- LCCN
- OCLC
- Sirsi Catalog Key
- solrID
6/16/2020