Consider need for new superclasses (Thing, Agent, Entity)

[jpmckinney]

e.g. owl:Thing, foaf:Agent, prov:Entity.

In OpenCorporates, it's sometimes unknown whether something is a Person or Organization. See openc-schema. The issue with using "Agent" in their use case is that a mutual fund, for example, doesn't have agency.

For such use cases, it may be useful to recommend an appropriate class for entities that is more generic than Person or Organization.

[akuckartz]

Can unions be allowed? See #118 for a use case for a union of Organization and Person.

[jpmckinney]

I think it's simpler (especially outside RDF) to declare an explicit superclass than to refer to an anonymous class that is the union of other classes.