For public Messages, Zero utilizes a Member's social graph to determine which Message data to store and replicate. Given that each Node announces which Nodes they publicly follow, zOS can arrange the application state into a graph of who follows who. By default, Zero sets a graph depth of two, meaning that Messages will be downloaded from those followed by who you follow. This is a useful heuristic to establish trust between Peers that was pioneered by Secure Scuttlebutt.