This CEN Workshop Agreement (CWA) presents the Simple Publishing Interface (SPI), a protocol for publishing digital objects or their metadata to repositories. This protocol is designed to facilitate the transfer of metadata and content from tools that produce learning materials to applications that manage learning objects and metadata, but is also applicable to the publication of a wider range of digital objects.The objective is to develop a practical approach towards interoperability between repositories for learning and applications that produce or consume educational materials. Examples of repositories for learning are educational brokers, knowledge pool