module rentals is

  ;; This is actually a US VIN
  import cids:VehicleIdentificationNumber

  import xml

  @xml:base = <https://example.org/v/rentals>
  @dc:version = 2

  entity Class

  union RentalClass of
    Compact
    UtilityVehicle
    Luxury
  end

  entity Vehicle is
    @skos:prefLabel = "Vehicle"@en

    identity vin -> VehicleIdentificationNumber

    ref rentalClass -> {1} Class
  end

  structure VehicleInformation is
    make -> xsd:string
    model -> xsd:string
    year -> xsd:integer is
      @xsd:minValue = 2000
      @xsd:maxValue = 3000
    end
  end

  entity Location

  entity Customer

  entity Booking is
    identity bookingCode -> unknown

    group
      ref bookingClass -> {1} Class
      ref vehicle -> {0..1} Vehicle
      ref from -> Location
    end
    ref customer -> {1} Customer
  end

end