Create a DNA server that uses a REST-based API, allowing client applications to access and use the repository using HTTP for protocol/transport.

AtomPub is also very interesting (as it is RESTful) for a message structure, but it doesn't currently support hierarchical data. And although one could build a repository to be flatter (or at least exposed though collections; see how Bento does it: http://www.filemaker.com/bento/), it may be difficult to have no way of interacting with the hierarchical data. Bento and iTunes both show how powerful user-defined collections (and "smart collections") can be, so maybe adopting a collection-only approach would work (at least for remote access).