Letter is a type of Document. Document is related to Degree. Degree is related to Graduate. 
Tap is a type of Tool. Tap is related to Time. Time is related to Punishment. Punishment is related to Conviction. 
Letter --IsA--> Document <--RelatedTo--> Degree <--RelatedTo--> Graduate 
Tool <--IsA-- Tap <--RelatedTo--> Time <--RelatedTo--> Punishment <--RelatedTo--> Conviction 