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
{
			return null;
		}
		return IReportElementConstants.RESULTSET_COLUMN_PREFIX
				+ "[\"" + DEUtil.escape( columnName ) + "\"]";
	}
	/**
	 * Relativizes the path against this base path.
	 * 
	 * @param basePath
	 *            the base path
	 * @param path
	 *            the path to convert
	 * @return The relative path based on the base path if it is possible, or
	 *         the original path
	 * 
	 */
	public static String getRelativedPath( String basePath, String path )
	{
		return URIUtil.getRelativePath( new File( basePath ).getParent( ), path );
	}
	/**
	 * Returns the handle of the action of the given element.
	 * 
	 * @param element
	 *            the element handle
	 * @return the handle of the action, or null if the element is not a proper
	 *         type
	 */
	public static ActionHandle getActionHandle( ReportItemHandle element )