Stump's three criteria for a distributed system has a partial-truth in it that might confuse people (and perhaps he himself is confused.) A distributed system can work just fine if there is a master, as long as the system does not rely upon that node always remaining the master and/or has no way to elect a new master if the old master can no longer connect to a quorum of the nodes in the system. Whenever you see nodes described as the "master" this is usually a strong indicator that the system is not really a distributed system, but you have to dig a bit deeper to make sure.