# 07.b-aggregate-relation-boundary-model

- [x] documentation slot exists
- [x] relation and boundary are explained as separate axes
- [x] join is explained as the third axis
- [x] metadata path carries `kind`, `boundary`, and `join`
- [x] runtime aggregate assembly distinguishes `association + external`
- [x] runtime aggregate assembly uses `direct` and `reverse`
- [x] runnable sample source exists
- [x] build succeeds
- [x] one aggregate load route works
- [x] aggregate search route works
- [x] README explains the difference among `OrderLine`, `ShipmentOrder`, and `User`
