Bug 177504 Engine doesn't provide SubQuery for extended item
Engine doesn't provide SubQuery for extended item, so chart can't use container's binding to execute the query. If possible, engine could provide an option for extended item to choose whether engine could create the query, so extended item won't create SubQuery by itself.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/data/dte/ReportQueryBuilder.java
*/
		private void transformExpressions( ReportItemDesign item,
				IBaseQueryDefinition query, String groupName )
		{
			if ( query != null )
			{
				ITotalExprBindings totalExpressionBindings = getNewExpressionBindings( item, query, groupName );
				addNewColumnBindings( query, totalExpressionBindings );
				replaceOldExpressions( item, totalExpressionBindings );
			}
		}
		
		/**
		 * Transfer the old expression to column dataBinding and bind it to the Query.
		 * And create a news expression to replace the old expression.
		 * @param expr expression to be transfered.
		 * return the transfered expression
		 */
		protected String transformExpression( String expr,
				IBaseQueryDefinition query, String groupName )
		{
			if ( expr == null )
			{
				return null;
			}
			if ( query != null )
			{
				List expressions = new ArrayList( );
				expressions.add( expr );	
				ITotalExprBindings totalExpressionBinding = expressionUtil