Lee-W commented on issue #59294:
URL: https://github.com/apache/airflow/issues/59294#issuecomment-3950237603

   A few concrete scenarios for `to_downstream(self) -> str | Iterable[str]`:
   
   * Weekly model training --> daily inference: ML model that's expensive to 
train (only needs retraining weekly) but runs inference daily against fresh 
data. When weekly partition completes, it needs to enable 7 daily inference 
partitions.
   * Weekly data deliver --> daily processing: External vendor provides weekly 
data files (contractually they only deliver weekly), but business needs daily 
processing/reporting. When the weekly file arrives, kick of 7 daily processing 
jobs for the week that just completed. 
   * Weekly aggregations --> daily dashboard: Expensive weekly rollups that get 
servedthrough a daily-sliced dashboard or API.
   
   
   For these to work, `to_downstream("2026-W10")` would need to return 
something like: `["2026-03-04", "2026-03-05", "2026-03-06", "2026-03-07", 
"2026-03-08", "2026-03-09", "2026-03-10"]`
   
   The tricky part is there are two different temporal relationships:
   
   Backward looking: Weekly W10 (March 4-10) enables 7 daily partitions WITHIN 
that week (March 4-10). All 7 would trigger at once when weekly completes.
   Forward-looking: Weekly W10 enables the NEXT 7 daily partitions (March 
11-17). They trigger according to their own schedule as each data arrives. 


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