Bug 202254 Exception is thrown when category values are null and type of X axis is set to DateTime
chart/org.eclipse.birt.chart.engine/src/org/eclipse/birt/chart/model/data/DataFactory.java
*/
	Query createQuery( );
	/**
	 * Returns a new object of class '<em>Rule</em>'.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @return a new object of class '<em>Rule</em>'.
	 * @deprecated only reserved for compatibility
	 */
	Rule createRule( );
	/**
	 * Returns a new object of class '<em>Sample Data</em>'.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @return a new object of class '<em>Sample Data</em>'.
	 * @generated
	 */
	SampleData createSampleData( );
	/**
	 * Returns a new object of class '<em>Series Definition</em>'.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @return a new object of class '<em>Series Definition</em>'.
	 * @generated
	 */
	SeriesDefinition createSeriesDefinition( );
	/**
	 * Returns a new object of class '<em>Series Grouping</em>'.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @return a new object of class '<em>Series Grouping</em>'.
	 * @generated
	 */
	SeriesGrouping createSeriesGrouping( );