Price is related to Gas. Gas is related to Commodity. 
Carrier is related to Sheep. Sheep is related to Origin. Origin is related to Species. Species is related to Class. 
Price <--RelatedTo--> Gas <--RelatedTo--> Commodity 
Carrier <--RelatedTo--> Sheep <--RelatedTo--> Origin <--RelatedTo--> Species <--RelatedTo--> Class 