Bug 136740 Error exporting data from a grouped report.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/impl/ExprManagerUtil.java
{
	private ExprManagerUtil(){}
	
	/**
	 *	This method tests whether column bindings in ExprManager is valid or not.
	 * 
	 * @param exprManager
	 * @return
	 * @throws DataException
	 */
	public static void validateColumnBinding( ExprManager exprManager )
			throws DataException
	{
		testDependencyCycle( exprManager ); 
		testGroupNameValidation( exprManager);
	}
	/**
	 *	Test whether high level group keys are depended on low level group keys.
	 * 
	 * @param exprManager
	 * @return
	 * @throws DataException