Rock is related to Formation. Line is a type of Formation. Painter is a type of Line. 
Comparison is related to Side. Side is a different concept from Corner. Corner is related to Dark. 
Rock <--RelatedTo--> Formation <--IsA-- Line <--IsA-- Painter 
Comparison <--RelatedTo--> Side <--DistinctFrom--> Corner <--RelatedTo--> Dark 