PartialDeliveryIndicator vs BackOrderAllowedIndicator

Dear all,

When and how should these indicators be used in the Line Item Delivery ?

Suppose that I allow my supplier to ship all quantities of an item  that are available on the requested data and ship the remaining quantities on a later date a, what values should these indicators have in my purchase order ?

What if I want my supplier to ship what is available on the requested data and cancel the remaining part ?

regards
Danny