Call is related to Voice. Voice can be used for Communicate. Communicate is related to Prayer. 
Possibility is derived from Ability. Skill is a type of Ability. Skill is related to Expertise. 
Call <--RelatedTo--> Voice --UsedFor--> Communicate <--RelatedTo--> Prayer 
Possibility --DerivedFrom--> Ability <--IsA-- Skill <--RelatedTo--> Expertise 