A diagram showing a directed acyclic graph where different authors published their operations in, every operation is a node in the graph, the edges point at the previously "seen" operations of all authors. We can “lock in” the group state from this moment on and agree on finality: Every change which will be applied into that “past” will be considered byzantine behaviour and illegal. This “fork the past” we also call equivocation and consensus protocols like that can help us to detect and mitigate them.