Each Dat is controlled by an append-only log. When you swarm a dat, you poll for updates to the log via UDP, which is low cost. (I think Mafintosh may have put

Each Dat is controlled by an append-only log. When you swarm a dat, you poll for updates to the log via UDP, which is low cost. (I think Mafintosh may have put in a push mechanism too.) So yes, you are notified. That's why Beaker is able to do live reloading.