So for first position we have a tie between Document B and E .
Document C and F don`t specify any ordering.
Document D and <no-id> says process me last but Document <no-id> also specifies that process me before document C.
So at first position we can have either B or E.
Document <no-id> can not be processed at last.
I want to know whether the order B,E,<no-id>,C,F,D is possible or not.
It looks to be a possible order of processing as it satisfies all <ordering> constraints.