This illustration shows an aggregate object mapping between source object `Employee` and target object `Period` and between source object Project and object `Period`. The `Employee` attribute `employPeriod` is mapped by an aggregate object mapping to target object `Period`. This mapping associates `Period` attribute `startDate` with `EMPLOYEE` table field `START_DATE` and `Period` attribute `endDate` with `EMPLOYEE` table field `END_DATE`. The `Project` attribute `projectPeriod` is mapped by an aggregate object mapping to target object `Period`. This mapping associates `Period` attribute `startDate` with `PROJECT` table field `S_DATE` and `Period` attribute `endDate` with `PROJECT` table field `E_DATE`.