Bug 136270 Group's data binding column can only be used by the group itself
If you add some data binding columns to a group, these columns can only be used by this group itself. It should has a way to make the child can use the parent group's data binding column.
UI/org.eclipse.birt.report.designer.core/src/org/eclipse/birt/report/designer/util/DEUtil.java
{
			SlotHandle slotHandle = parent.getSlot( DEUtil.getDefaultSlotID( parent ) );
			if ( slotHandle != null )
			{
				return slotHandle.getCount( );
			}
			return -1;
		}
		return DEUtil.findPos( parent, element.getContainerSlotHandle( )
				.getSlotID( ), element );
	}
	/**
	 * Map GUI defined property key to DE defined property key
	 * 
	 * @param key
	 * @return DE defined property key
	 */
	public static String getGUIPropertyKey( String key )
	{
		if ( key != null )
		{
			return (String) propertiesMap.get( key );
		}
		return null;
	}
	/**
	 * Transform other units to pixel.
	 * 
	 * @param handle
	 *            DimensionHandle of model to keep the measure and units.