Observer is a type of Person. Observe is derived from Observer. Observe is related to Gaze. 
Drag is a type of Pull. Pull is related to Shade. Shade is related to Area. Area is related to Bank. 
Person <--IsA-- Observer <--DerivedFrom-- Observe <--RelatedTo--> Gaze 
Drag --IsA--> Pull <--RelatedTo--> Shade <--RelatedTo--> Area <--RelatedTo--> Bank 