Federated object storage with access control and event subscribtion

Hi Federated Social Web group,

I'm a computer science student in Karlsruhe, Germany at the KIT[0]. I'm
interested in developing a protocol to share "objects" in a federated
network and I'm going to do this as my Bachelor thesis.
At the moment I'm trying to find related work or an existing protocol which
does this already and did not have any luck so far. As my motivation is to
serve the federated social web, I was told to look at the work of this
group but could not find anything either.
My question is now, does anybody of you know a protocol or a system that
allows users to store objects or data in a federated network, set
permissions for other users which are not on the same server and can notify
about updates (push)?
Thank you for your time.

Regards
Felix Maurer

[0] http://www.kit.edu