Jobs of the type OAI CONTENT VALIDATION include rules that will be applied to the repository’s RECORDS. For example, one such rule might be to check if a dc:identifier field is present in the record being checked.
Jobs of the type OAI USAGE VALIDATION include rules that check the correct implementation of the OAI-PMH protocol. For example, one such rule might be to check if the repository answers correctly to incremental delivery requests (using from/until in ListIdentifiers and ListRecords requests).