N::Continent { name: String } N::Country { name: String, currency: String, population: I64, gdp: F64 } N::City { name: String, description: String, zip_codes: [String] } E::Continent_to_Country { From: Continent, To: Country, Properties: { } } E::Country_to_City { From: Country, To: City, Properties: { } } E::Country_to_Capital { From: Country, To: City, Properties: { } }