Duty is related to Officer. Officer is related to Army. you are likely to find Leader in/at/on Army. Leader is related to Principal. 
Mud is a type of Dirt. Dirt is related to Garbage. 
Duty <--RelatedTo--> Officer <--RelatedTo--> Army <--AtLocation-- Leader <--RelatedTo--> Principal 
Mud --IsA--> Dirt <--RelatedTo--> Garbage 