Arm is a type of Projection. you are likely to find Arm in/at/on House. you are likely to find Jar in/at/on House. 
Spouse is a type of Relative. Relative is related to Sister. 
Projection <--IsA-- Arm --AtLocation--> House <--AtLocation-- Jar 
Spouse --IsA--> Relative <--RelatedTo--> Sister 