Bug 174872 Clean up chart model
The chart model contains unused attributes and components. Those just make it difficult to understand the model architecture, so they should be removed from the schema, and the EMF classes must re-generated. Examples are: ChartPreferences, Rule. We need to analyze the model to find out all unused ones. Note that this should not break backward compatibility, otherwise just make them deprecated.
chart/org.eclipse.birt.chart.engine/src/org/eclipse/birt/chart/model/data/DataFactory.java
*/
	DataSet createDataSet( );
	/**
	 * Returns a new object of class '<em>Date Time Data Element</em>'. <!-- begin-user-doc --> <!-- end-user-doc
	 * -->
	 * 
	 * @return a new object of class '<em>Date Time Data Element</em>'.
	 * @generated
	 */
	DateTimeDataElement createDateTimeDataElement( );
	/**
	 * Returns a new object of class '<em>Date Time Data Set</em>'.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @return a new object of class '<em>Date Time Data Set</em>'.
	 * @generated
	 */
	DateTimeDataSet createDateTimeDataSet( );
	/**
	 * Returns a new object of class '<em>Difference Data Set</em>'.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @return a new object of class '<em>Difference Data Set</em>'.
	 * @generated
	 */
	DifferenceDataSet createDifferenceDataSet( );
	/**
	 * Returns a new object of class '<em>Gantt Data Set</em>'.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @return a new object of class '<em>Gantt Data Set</em>'.