The previous article ends with a dict full of the latest values. That is a working state, not a record: restart the process and everything before the restart is gone. This article is the step after — deciding what to keep, for how long, at what resolution, and which numbers actually answer a question anyone cares about.

It matters more than it sounds, because a single instant reading is nearly useless. "Occupied, still, right now" is a fact you could get by looking into the room. The facts that are worth keeping are the ones nobody can observe: how long she slept, how often she got up, whether tonight's activity looks like last month's.…