Assume is a type of Move. Move is a type of Decision. Decision is related to Choose. Buy entails/necessarily involves Choose. 
Top is related to Table. Table is related to Seat. Seat is related to Area. 
Assume --IsA--> Move --IsA--> Decision <--RelatedTo--> Choose <--Entails-- Buy 
Top <--RelatedTo--> Table <--RelatedTo--> Seat <--RelatedTo--> Area 