Hazard is related to Material. Material is related to Concrete. Concrete is related to Steel. 
Leaf is related to Item. Item is related to Production. Production is related to Pro. 
Hazard <--RelatedTo--> Material <--RelatedTo--> Concrete <--RelatedTo--> Steel 
Leaf <--RelatedTo--> Item <--RelatedTo--> Production <--RelatedTo--> Pro 