Rule 1 : First task should not have predecessors, Last task should not have successors.
Rule 2 : Except first and last tasks, every task must have both predecessors and successors.
Rule 3 : Project Summary task, Summary task should not have predecessors, successors
Rule 4 : Resource should not be allocated for Milestone.
Rule 5 : Resource should not be allocated for Project summary tasks and summary tasks.
Rule 6 : Project summary task and summary task duration should not be mentioned manually, it should calculate task duration automatically.
Rule 7 : All sub tasks must have duration > 0 day except milestone. Milestone should be have duration of 0 day.