This European Standard specifies the Simple Publishing Interface (SPI), an abstract protocol for publishing digital content and/or the metadata that describes it into repositories in a way that preserves the references between the two. This protocol is designed to facilitate the transfer of learning materials from tools that produce learning materials to applications that manage learning objects and metadata. It is also applicable to the publication of a wider range of digital objects. The objectives behind SPI are to develop practical approaches towards interoperability between repositories for learning and applications that produce or consume educational materials. Examples of repositories for learning include educational brokers, knowledge pools, institutional repositories, streaming video servers, etc. Examples of applications that produce these educational materials are query and indexation tools, authoring tools, presentation programs, content packagers, etc. Whilst the development of the SPI specification draws exclusively on examples from the education sector, it is recognised that the underlying requirement to publish content and metadata into repositories crosses multiple application domains. This abstract model has been designed to be implemented using existing specifications such as v1.3 Simple Web-service Offering Repository Deposit (SWORD) profile [SWORD], Package Exchange Notification Services [PENS] and the publishing specification that was developed in the ProLearn Network of Excellence [PROLEARN SPI]. The intent of this work is thus not to create yet another specification but to create a model that can be bound to existing technologies in order to make sure that these technologies are used in a way that takes into account requirements specific to the learning domain, where it is necessary to publish both content and metadata that references it in a way that preserves these references. The SPI model enumerates the different messages that are interchanged when publishing metadata and content.