The SONEX Workgroup, led by Pablo de Castro and Peter Burnhill, addresses interoperability in repository systems, comparing its pragmatic approach to the theoretical frameworks of dl.org. Established during the Institutional Repositories Workshop in 2009, SONEX focuses on use-case scenarios for publisher deposits, CRIS/institutional repository integration, and funder mandates. Current tasks include supporting selected JISC projects and disseminating information for international cooperation.