Bug 317417 [Model] StackElement should be abstract and interface
StackElement is only a marker for improved containment hierarchies. We should at least make it abstract but also as an interface like WindowElement, ...
bundles/org.eclipse.e4.ui.model.workbench/src/org/eclipse/e4/ui/model/application/ui/basic/impl/BasicPackageImpl.java
public static final int PART__VISIBLE = ApplicationPackageImpl.CONTRIBUTION_FEATURE_COUNT + 7;
	/**
	 * The feature id for the '<em><b>Parent</b></em>' container reference.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @generated
	 * @ordered
	 */
	public static final int PART__PARENT = ApplicationPackageImpl.CONTRIBUTION_FEATURE_COUNT + 8;
	/**
	 * The feature id for the '<em><b>Container Data</b></em>' attribute.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @generated
	 * @ordered
	 */
	public static final int PART__CONTAINER_DATA = ApplicationPackageImpl.CONTRIBUTION_FEATURE_COUNT + 9;
	/**
	 * The feature id for the '<em><b>Cur Shared Ref</b></em>' reference.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @generated
	 * @ordered
	 */
	public static final int PART__CUR_SHARED_REF = ApplicationPackageImpl.CONTRIBUTION_FEATURE_COUNT + 10;
	/**
	 * The feature id for the '<em><b>Visible When</b></em>' containment reference.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @generated