This naturally includes support for maintaining an appropriate consistency between a cache and its sources. This might include ways for a client to pick a good replica. This might include fine-grained delegation of rights to caches. This may interact with the WebDAV extension. Support for privacy.
Limited trust exposures.
That is, how little trust has to be extended to other parties for a given party to get its job done. Support for nested and recursive RPCs. It would be a shame if the RPC mechanism prohibited, or introduced deadlocks in, these cases. For embedded applications, where a client or server can't call on much CPU, memory, disk, etc. Support for internationalization.