/**
  * Get's the repository object ID of a parent object, if possible
  * 
  * see ilWebAccessChecker 
  */
 function getParentObjectIdForUsage($a_usage, $a_include_all_access_obj_ids = false)
 {
     if (is_int(strpos($a_usage["type"], ":"))) {
         $us_arr = explode(":", $a_usage["type"]);
         $type = $us_arr[1];
         $cont_type = $us_arr[0];
     } else {
         $type = $a_usage["type"];
     }
     $id = $a_usage["id"];
     $obj_id = false;
     switch ($type) {
         // RTE / tiny mce
         case "html":
             switch ($cont_type) {
                 case "qpl":
                     // Question Pool *Question* Text (Test)
                     include_once "./Modules/TestQuestionPool/classes/class.assQuestion.php";
                     $qinfo = assQuestion::_getQuestionInfo($id);
                     if ($qinfo["original_id"] > 0) {
                         include_once "./Modules/Test/classes/class.ilObjTest.php";
                         $obj_id = ilObjTest::_lookupTestObjIdForQuestionId($id);
                         // usage in test
                     } else {
                         $obj_id = $qinfo["obj_fi"];
                         // usage in pool
                     }
                     break;
                 case "spl":
                     // Question Pool *Question* Text (Survey)
                     include_once "./Modules/SurveyQuestionPool/classes/class.SurveyQuestion.php";
                     $quest = SurveyQuestion::_instanciateQuestion($id);
                     if ($quest) {
                         if ($quest->getOriginalId() > 0) {
                             $obj_id = $quest->getSurveyId();
                         } else {
                             $obj_id = $quest->getObjId();
                             // usage in pool
                         }
                         unset($quest);
                     }
                     break;
                 case "exca":
                     // Exercise assignment
                     $returned_pk = $a_usage['id'];
                     // we are just checking against exercise object
                     include_once 'Modules/Exercise/classes/class.ilObjExercise.php';
                     $obj_id = ilObjExercise::lookupExerciseIdForReturnedId($returned_pk);
                     break;
                 case "frm":
                     // Forum
                     $post_pk = $a_usage['id'];
                     include_once 'Modules/Forum/classes/class.ilForumPost.php';
                     include_once 'Modules/Forum/classes/class.ilForum.php';
                     $oPost = new ilForumPost($post_pk);
                     $frm_pk = $oPost->getForumId();
                     $obj_id = ilForum::_lookupObjIdForForumId($frm_pk);
                     break;
                     // temporary items (per user)
                 // temporary items (per user)
                 case "frm~":
                 case "exca~":
                     $obj_id = $a_usage['id'];
                     break;
                     // "old" category pages
                 // "old" category pages
                 case "cat":
                     // InfoScreen Text
                 // InfoScreen Text
                 case "tst":
                 case "svy":
                     // data collection
                 // data collection
                 case "dcl":
                     $obj_id = $id;
                     break;
             }
             break;
             // page editor
         // page editor
         case "pg":
             switch ($cont_type) {
                 case "qpl":
                     // Question Pool Question Pages
                     include_once "./Modules/TestQuestionPool/classes/class.assQuestion.php";
                     $qinfo = assQuestion::_getQuestionInfo($id);
                     if ($qinfo["original_id"] > 0) {
                         include_once "./Modules/Test/classes/class.ilObjTest.php";
                         $obj_id = ilObjTest::_lookupTestObjIdForQuestionId($id);
                         // usage in test
                     } else {
                         $obj_id = $qinfo["obj_fi"];
                         // usage in pool
                     }
                     break;
                 case "lm":
                 case "dbk":
                     // learning modules
                     include_once "./Modules/LearningModule/classes/class.ilLMObject.php";
                     $obj_id = ilLMObject::_lookupContObjID($id);
                     break;
                 case "gdf":
                     // glossary definition
                     include_once "./Modules/Glossary/classes/class.ilGlossaryDefinition.php";
                     include_once "./Modules/Glossary/classes/class.ilGlossaryTerm.php";
                     $term_id = ilGlossaryDefinition::_lookupTermId($id);
                     $obj_id = ilGlossaryTerm::_lookGlossaryID($term_id);
                     break;
                 case "wpg":
                     // wiki page
                     include_once 'Modules/Wiki/classes/class.ilWikiPage.php';
                     $obj_id = ilWikiPage::lookupObjIdByPage($id);
                     break;
                 case "sahs":
                     // sahs page
                     // can this implementation be used for other content types, too?
                     include_once './Services/COPage/classes/class.ilPageObject.php';
                     $obj_id = ilPageObject::lookupParentId($id, 'sahs');
                     break;
                 case "prtf":
                     // portfolio
                     include_once "Modules/Portfolio/classes/class.ilPortfolioPage.php";
                     $obj_id = ilPortfolioPage::findPortfolioForPage($id);
                     break;
                 case "prtt":
                     // portfolio template
                     include_once "Modules/Portfolio/classes/class.ilPortfolioTemplatePage.php";
                     $obj_id = ilPortfolioTemplatePage::findPortfolioForPage($id);
                     break;
                 case "blp":
                     // blog
                     include_once './Services/COPage/classes/class.ilPageObject.php';
                     $obj_id = ilPageObject::lookupParentId($id, 'blp');
                     break;
                 case "crs":
                 case "grp":
                 case "cat":
                 case "fold":
                 case "root":
                     // repository pages
                     $obj_id = $id;
                     break;
             }
             break;
             // Media Pool
         // Media Pool
         case "mep":
             $obj_id = $id;
             break;
             // News Context Object (e.g. MediaCast)
         // News Context Object (e.g. MediaCast)
         case "news":
             include_once "./Services/News/classes/class.ilNewsItem.php";
             $obj_id = ilNewsItem::_lookupContextObjId($id);
             break;
     }
     return $obj_id;
 }