On my forms, I have some list with attribute who are marked as mandatory in my Business Data Model. My users have to fill the list by himself (for example, a list of item to buy (the number of elements can be dynamic, that's why I use container)).
When i create a container who will contain the mandatory list, the user can submit the form without fill a single element of my list.
That's because the mandatory attribute only appear when my users add the first element of the list on the container.
You can see what i'm trying to explain here :