Hi all, I didn't think I'd be answering many threads on this list but when I saw the points about "moons of Uranus" and "cities through history" examples I couldn't resist mentioning the LIDO Schema (www.lido-schema.org) and the CIDOC-CRM ontology that it's based on (www.cidoc-crm.org/) - they have the descriptive power and range to cope with alternative historical viewpoints and "takes" on entities that you might need. Happy to discuss further.