Middle is a type of Point. Point is related to Average. Average is related to Plain. Plain is a synonym of Complain. 
Worth is similar to Valuable. Diamond can be Valuable. Diamond is a type of Mineral. Mineral is related to Element. 
Middle --IsA--> Point <--RelatedTo--> Average <--RelatedTo--> Plain <--Synonym--> Complain 
Worth <--SimilarTo--> Valuable <--HasProperty-- Diamond --IsA--> Mineral <--RelatedTo--> Element 