@namespace(uri="vehicles", prefix="")
package vehicles;


class Vehicle {
	attr String reg;
	attr String colour;
	val Wheel[*] wheels;
	val Engine engine;
}

abstract class Engine {
	attr int cc;
}

class DieselEngine extends Engine {
	
}

class PetrolEngine extends Engine {
	
}

class Wheel {
	attr int size;
}