Its own, I guess? ConceptNet is really not so much about having an upper ontology, it's about relations between natural language words and phrases. Its set of relations is effectively a superset of WordNet's.

Hmm but for example. If I search "harry potter", one of the things I get is "harry potter is defined as... " "boy who lives under the stair". What can I do with this? "boy", "lives", "under", and "stair", while present in conceptnet, have no logical relation to anything else...