Indicator is a type of Signal. Signal is related to Stop. Stop is related to Song. Song is related to Material. 
Complete is a different concept from Empty. Exhaust is a type of Empty. 
Indicator --IsA--> Signal <--RelatedTo--> Stop <--RelatedTo--> Song <--RelatedTo--> Material 
Complete <--DistinctFrom--> Empty <--IsA-- Exhaust 