Time

From your world. Late-arriving facts and dimensions in Kimball; how long to hold a window open before you trust the number

Explain to a Kimball modeler who reprocesses "the last few days" every night:

"What is a watermark, why must it only move forward, and how is allowedLateness the same decision as my dbt lookback window?"

Rubric (self-check — aim for 5/6)

Distinguishes event time from processing time. Says why they diverge (network, retries, buffering).
Defines a watermark as a completeness claim: "seen all events with event time ≤ W".
States the monotonic / non-decreasing rule and why (closed windows must not re-open).
Gives the bounded-out-of-orderness formula W = maxEventTime − allowedLateness.
Classifies events as on-time / late-accepted / dropped relative to W and the grace window. Says that late events in auditable data go to a side output, not to a silent drop.
Maps allowedLateness to the dbt lookback window / Kimball late-arriving facts.