OAI-PMH is the Open Archives Initiative protocol for harvesting metadata from repositories. Six verbs over HTTP let an aggregator discover what a repository holds and collect its records incrementally. It is how institutional repositories became collectively searchable without a central database.
OAI-PMH
OAI-PMH is a six-verb HTTP protocol from 2001 that solved federated discovery for scholarly repositories and has needed remarkably little revision since. Identify, ListRecords, GetRecord and three more — that is the entire surface.
- Six verbs - A deliberately tiny protocol, which is why implementations are consistent.
- Incremental harvesting - Datestamp-scoped requests, so an aggregator collects only what changed.
- Set-based selection - Repositories expose logical subsets a harvester can target.
- Dublin Core minimum - One mandatory metadata format guarantees any harvester can read any repository.
OAI-PMH is worth studying next to modern discovery efforts. It is older than REST as common practice, it is boring, and it works — which is part of why the repository segment in The State of Education & EdTech APIs publishes machine-readable contracts at 70.8%, the highest of any segment in that market. A protocol everybody implements the same way is worth more than a richer one everybody implements differently.
Referenced in API Evangelist papers
This standard shows up in my published research. These reports read the machine-readable evidence provider by provider — and put this standard in the context of a real sector.
The State of Education & EdTech APIs
A six-verb protocol from 2001 underneath the segment publishing machine-readable contracts at 70.8% — the highest in the education market.
