CRM_Utils_Migrate_Export - Doc comment

CRM/Utils/Migrate/Export.php

@@ -36,6 +36,20 @@ class CRM_Utils_Migrate_Export {
 
   const XML_VALUE_SEPARATOR = ":;:;:;";
 
+  /**
+   * @var array description of export field mapping
+   *
+   * @code
+   * 'exampleEntityMappingName' => array(
+   *   'data' => array(),                     // placeholder; this will get filled-in during execution
+   *   'name' => 'CustomGroup',               // per-item XML tag name
+   *   'scope' => 'CustomGroups',             // container XML tag name
+   *   'required' => FALSE,                   // whether we *must* find records of this type
+   *   'idNameFields' => array('id', 'name'), // name of the (local/autogenerated) "id" and (portable) "name" columns
+   *   'idNameMap' => array(),                // placeholder; this will get filled-in during execution
+   * ),
+   * @endcode
+   */
   protected $_xml;
 
   function __construct() {