In 2011, Confederation of Open Access Repositories (COAR) published the paper, The Case for Interoperability for Open Access Repositories.
Open Access repositories, whose number has been steadily rising, are an important component of the global e-Research infrastructure. The real value of repositories lies in the potential to interconnect them to create a network of repositories, a network that can provide unified access to research outputs and be (re-) used by machines and researchers. However, in order to achieve this potential, we need interoperability. The purpose of this paper is to provide a high-level overview of interoperability of Open Access repositories, identify the major issues and challenges that need to be addressed, stimulate the engagement of the repository community and launch a process that will lead to the establishment of a COAR roadmap for repository interoperability.