It comes up quite a bit if you have repeated data in batches where the batches are a first class concept. Any relations need to be qualified by both normal fk i

It comes up quite a bit if you have repeated data in batches where the batches are a first class concept. Any relations need to be qualified by both normal fk id and batch id, or else you bring back across all batches. Think something like measurements samples that come in an envelope with metadata, or account updates that come in a statement, that kind of thing.