I will try to explain this scenario.
Order
OrderItem
These are not related in database using foreign key.
I am building a business component for UI that has one Order & corresponding multiple OrderItem in the same window entered.
So my business component object should have
an OrderEntity instance & and a collection of OrderItemEntity.
fetch, add, update all are managed by the business component using UnitofWork.
call validations for Order & OrderItem in the preferred order.
OR
define the relation in genpro designer between Order & OrderItem.
It constructs prefetch path, relations. so fetch, add, update happens for OrderItem as well. so the adapter can call Order.update to take care of all changes to be updated using unitofwork
have code in Order to call validations for OrderItem as well.