The stages
Bi-temporal by construction
The store records both valid time (when a fact was true in the world) and transaction time (when the graph learned it).as_of(valid_t, tx_t) returns the graph
as it was believed at a point in time — which is what makes a KG auditable rather than
merely current. A correction does not erase what the graph previously asserted; it adds a
new transaction over the same valid-time span.