Uses
Commercial search engines have started using OAI-PMH to acquire more resources. Google is using OAI-PMH to harvest information from the National Library of Australia Digital Object Repository. In 2004, Yahoo! acquired content from OAIster (University of Michigan) that was obtained through metadata harvesting with OAI-PMH. Google did accept OAI-PMH as part of their Sitemap Protocol, though decided to stop doing so in 2008. Wikimedia uses an OAI-PMH repository to provide feeds of Wikipedia and related site updates for search engines and other bulk analysis/republishing endeavors. Especially when dealing with thousands of files being harvested every day, OAI-PMH can help in reducing the network traffic and other resource usage by doing an incremental harvesting. NASA's Mercury: Metadata Search System uses OAI-PMH to index thousands of metadata records from Global Change Master Directory (GCMD) every day.
The mod_oai project is using OAI-PMH to expose content to web crawlers that is accessible from Apache Web servers.
Read more about this topic: Open Archives Initiative Protocol For Metadata Harvesting