From CUNY Academic Commons
“The Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH) is a low-barrier mechanism for repository interoperability. Data Providers are repositories that expose structured metadata via OAI-PMH. Service Providers then make OAI-PMH service requests to harvest that metadata. OAI-PMH is a set of six verbs or services that are invoked within HTTP.”
Harvesting from Digital Repositories
By “exposing” a digital collection’s metadata (i.e. publishing a url that can be used to access it), a repository can share its collections, as long as the metadata conforms to OAI-PMH standards. Harvestors can ingest the metadata, index it, and link to the urls that are contained within it.
For example, a web publishing tool such as Omeka can point at a OAI-PMH compliant digital collection in the Library of Congress, suck in the collection’s metadata and display it. Links to images may be clicked on via urls supplied within the metadata.