A domain is the entire set of data for a level of aggregation.
When a logical table is sourced from a set of fragments for a particular aggregation level.
Within a whole universe, measure aggregations can be calculated based on the set of fragments.
When some fragments are missing, the Oracle BI Server assumes that it does not have the whole universe of fragments, it would be incorrect to calculate aggregate rollups and in this case, the server returns NULL as measure aggregates.
Partial case: