Airplane can be used for Travel. Angle is a type of Travel. Angle is related to Slope. Slope is related to Rolling. 
Witness is related to Observer. Observer is a type of Expert. Technician is a type of Expert. Technician is a type of Professional. 
Airplane --UsedFor--> Travel <--IsA-- Angle <--RelatedTo--> Slope <--RelatedTo--> Rolling 
Witness <--RelatedTo--> Observer --IsA--> Expert <--IsA-- Technician --IsA--> Professional 