  In the emerging eScience environment, repositories of papers, datasets,
software, etc., should be the foundation of a global and natively-digital
scholarly communications system. The current infrastructure falls far short of
this goal. Cross-repository interoperability must be augmented to support the
many workflows and value-chains involved in scholarly communication. This will
not be achieved through the promotion of single repository architecture or
content representation, but instead requires an interoperability framework to
connect the many heterogeneous systems that will exist.
  We present a simple data model and service architecture that augments
repository interoperability to enable scholarly value-chains to be implemented.
We describe an experiment that demonstrates how the proposed infrastructure can
be deployed to implement the workflow involved in the creation of an overlay
journal over several different repository systems (Fedora, aDORe, DSpace and
arXiv).
