The Open Archives Initiative (OAI) is dedicated to solving problems of digital library interoperability. Its focus has been on defining simple protocols, most recently for the exchange of metadata from archives. The OAI evolved out of a need to increase access to scholarly publications by supporting the creation of interoperable digital libraries. As a first step towards such interoperability, a metadata harvesting protocol was developed to support the streaming of metadata from one repository to another, ultimately to a provider of user services such as browsing, searching, or annotation. This article provides an overview of the mission, philosophy, and technical framework of the OAI.