Bug 121498 When datasource/dataset deleted, the datasource/dataset property binding element haven't been deleted
When deleted the datasource/dataset, the datasource/dataset property binding element haven't been deleted. Expected result: This operation must be a transaction.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/DesignElementHandle.java
{
				DesignElementHandle h1 = (DesignElementHandle) arg0;
				DesignElementHandle h2 = (DesignElementHandle) arg1;
				String s1 = h1.getDisplayLabel( );
				String s2 = h2.getDisplayLabel( );
				return s1.compareTo( s2 );
			}
		} );
	}
	/**
	 * Returns whether the element is valid or not. An element may be valid even
	 * though it has some semantic errors.
	 * 
	 * @return <code>true</code> if this element is valid, otherwise
	 *         <code>false</code>.
	 */
	public boolean isValid( )
	{
		return getElement( ).isValid( );
	}
	/**
	 * Determines whether to show an error item on the element or not. Show an
	 * error item if the element is invalid or has semantic errors, otherwise
	 * not.
	 * 
	 * @return true if the element has semantic error or the element is invalid
	 */
	public boolean showError( )
	{
		return hasSemanticError( ) || !isValid( );