JSON Export mapping missing few attributes while calling REST service

I have 4 attributes in the JSON structure and out of them any one is mandatory but for REST service all 4 attributes should be send. 

But in my case only specified attributes are part of request message to the API. The minimum occurrence is default set to 0 in export mapping properties which I am not able to change also my entities are non persistent.

required schema to be sent {"name": "", "college": "", "department": "", "include_transactions": false}

as is scenario  {"department": "test", "include_transactions": false} (missed the name and college from the request message )