The graph is build incrementally by a series of signed updates. Each node & edge has a uuid that’s assigned at creation whose time is also recorded. Updates may contain nodes that have an already used UUID. In that situation, the node in the update is linked to the existing node with an EQUALS edge.
When calculating the node linked to by an EQUALS, the first occurrence of each attribute as the EQUALS links are walked in a breadth-first order according to creation time.
It is also possible that an update will contain a Spot with a path leading to it that is identical to a previous incarnation, but with a different uuid. In this situation,