@namespace(uri="OO", prefix="OO")
package OO;

class Model extends Package {
}

abstract class PackageableElement extends NamedElement {
  ref Package#contents ~package;
}

abstract class AnnotatedElement {
  val Annotation[*] annotations;
}

class Annotation {
  attr String key;
  attr String value;
}

abstract class NamedElement extends AnnotatedElement {
  attr String name;
}

class Package extends PackageableElement {
  val PackageableElement[*]#~package contents;
}

abstract class ~Classifier extends PackageableElement {
}

class ExternalClass extends ~Class {
}

class ~Class extends ~Classifier {
  ref ~Class#extendedBy ~extends;
  ref ~Class[*]#~extends extendedBy;
  val Feature[*]#owner features;
  attr Boolean isAbstract;
}

class Datatype extends ~Classifier {
}

abstract class Feature extends NamedElement {
  ref ~Class#features owner;
  ref ~Classifier type;
  attr VisibilityEnum visibility;
}

abstract class StructuralFeature extends Feature {
  attr Boolean isMany;
}

class Operation extends Feature {
  val Parameter[*]#owner parameters;
}

class Parameter extends NamedElement {
  ref ~Classifier type;
  ref Operation#parameters owner;
}

class Reference extends StructuralFeature {
}

class Attribute extends StructuralFeature {
}

enum VisibilityEnum {
  public = 1;
  private = 2;
}