Concepts and Collections are disjoint classes in SKOS. Having an instance of both is bad. This could happen typically if mapping properties are used on a Collection; since mapping properties have domain skos:Concept, this would make the Collection an instance of skos:Concept too.
Concepts and Collections are disjoint classes in SKOS. Having an instance of both is bad. This could happen typically if mapping properties are used on a Collection; since mapping properties have domain skos:Concept, this would make the Collection an instance of skos:Concept too.