Fable
The night watchman looks one stretch further each time
The city wall was very long, and the night watchmen originally handed over along fixed sections. The first team guarded from the East Gate to the bell tower, the second from the bell tower to the granary. The map was clean, and responsibility was clear.
Problems always arise at the boundaries. Someone planted a firestarter in front of the bell tower, and the east gate team said that was already close to the next segment; footprints behind the bell tower were found by the granary team, but they didn't know what had happened ahead.
The city lord first cut the road sections shorter. Night patrols became more detailed, handovers increased, and the record books piled up into small mountains. Many people knew only their own ten steps and still could not see the movements connected before and after.
Later he cut the road sections even longer. The context was sufficient, but each team carried too large a scope, and the truly anomalous steps were drowned in long reports. Short has short blind spots; long has long burdens.
An old night watchman proposed a simple approach: each team still walked a fixed length, but the next team started early from where the previous team had not yet finished. Keeping an overlap between the two teams meant the boundary was no longer a black hole.
In this way, a fire near the bell tower would appear in two night patrol records at the same time. The east gate team could see where it came from, and the granary team could also see where it was going. Duplication had a cost, but it was cheaper than missing danger at the boundary.
The castellan worried that records would pile up. The veteran night watchman said that overlap must not be greedy, and the window cannot be arbitrarily large. The more complex the path, the more the overlap must cover the minimum length over which a single matter continues across segments; otherwise it merely manufactures a sense of security on paper.
Later, city walls, river channels and warehouses all used this patrol method. Each record was independently readable, yet locked onto the previous and next records at one point, enough for investigators to reconstruct a continuous event. Only then did everyone understand that boundaries must be designed, not pretended not to exist. The old night watchman also reminded them that overlapping segments must be read carefully. If the next team merely copies them mechanically, there is more paper but not more eyes. Truly useful overlap is letting both teams understand what happened near the boundary, not writing the same sentence into the ledger twice. The city lord later applied this method to case files and account books. Whenever a matter might cross a boundary, leave it a little overlap so the next segment can pick up from the previous one. Later, during the review, everyone wrote this lesson into the daily rules: first look at where on the scene the outcome actually changed, then decide what to keep, repair or restrict.