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.