OAI-PMH (Open Archives Initiative Protocol for Metadata Harvesting) is a protocol for exposing metadata so it can be harvested and used by search services. The Open Archives Initiative (OAI) developed the protocol to provide an interoperability framework for e-print repositories, but it can be applied to a wide range of digital materials.
A ‘data provider’ builds an OAI-compliant repository and uses the protocol to expose its metadata. A ‘service provider’ then uses the same protocol to harvest the metadata. Typically the service provider harvests metadata from several sources. Once the metadata is aggregated, the service provider then uses it to provide services. A search service based on the aggregated metadata effectively allows users to cross-search the separate sources. However, as the metadata is aggregated in one place, the service provider has opportunities to enhance it and provide value-added services.

If you are not familiar with this protocol, a good place to start is the Open archives Initiative website.
A complete tutorial is available at Open Archives Forum: OAI for Beginners.
With regard to the Driver guidelines the following rules apply:


• The repository must be OAI-2.0 compliant and must conform to the specification on chapter “Use of OAI-PMH” on page 35 of the Driver Guidelines


• Existence of a repository identifier and use of the OAI identifier scheme


• If (and only if) the repository contains resources other than those which are mandatory in “PART A - Textual Resources”, an OAI-set is defined as that which identifies the collection of digital textual resources accessible in Open Access (see explanations “DRIVER Set naming”, “DRIVER Set Content definitions” and “Set Location” on pages 42-44 of the Driver Guidelines)



• Provisions for the change of Base-URL


• Completeness of Identify Response, including use of the optional Description statement


• Use persistent of Transient deleting strategy


• Use a batch size with corresponding resumption token expiration time.