Source for file HarmoniHierarchy.class.php

<?php
 
require_once(OKI2."/osid/hierarchy/Hierarchy.php");
require_once(HARMONI.'/oki2/hierarchy/HarmoniNode.class.php');
require_once(HARMONI.'/oki2/hierarchy/HierarchyCache.class.php');
require_once(HARMONI.'/oki2/hierarchy/HarmoniNodeIterator.class.php');
require_once(HARMONI.'/oki2/hierarchy/HarmoniTraversalInfo.class.php');
require_once(HARMONI.'/oki2/hierarchy/HarmoniTraversalInfoIterator.class.php');
require_once(HARMONI.'/oki2/hierarchy/DefaultNodeType.class.php');
 
/**
 * Hierarchy is a structure composed of nodes arranged in root, parent, and
 * child form.    The Hierarchy can be traversed in several ways to determine
 * the arrangement of nodes. A Hierarchy can allow multiple parents.  A
 * Hierarchy can allow recursion.  The implementation is responsible for
 * ensuring that the integrity of the Hierarchy is always maintained.
 * 
 * <p>
 * OSID Version: 2.0
 * </p>
 *
 * @package harmoni.osid_v2.hierarchy
 * 
 * @copyright Copyright &copy; 2005, Middlebury College
 * @license http://www.gnu.org/copyleft/gpl.html GNU General Public License (GPL)
 *
 * @version $Id: HarmoniHierarchy.class.php,v 1.22 2007/09/17 16:44:35 adamfranco Exp $
 */
 
class HarmoniHierarchy 
    extends Hierarchy {
 
    /**
     * The Id of this hierarchy.
     * @var object _id 
     * @access private
     */
    var $_id;
    
    
    /**
     * The display name of this hierarchy.
     * @var string _displayName
     * @access private
     */
    var $_displayName;
    
    
    /**
     * The description of this hierarchy.
     * @var string _description
     * @access private
     */
    var $_description;    
    
    /**
     * Constructor.
     *
     * @param object ID      $id    The Id of this Hierarchy.
     * @param string $displayName The displayName of the Hierarchy.
     * @param string $description The description of the Hierarchy.
     * @param boolean allowsMultipleParents This is true if the hierarchy will allow
     *  multiple parents.
     * @param ref object cache This is the HierarchyCache object. Must be the same
     *  one that all other nodes in the Hierarchy are using.
     * @access public
     */
    function HarmoniHierarchy($id, $displayName, $description, $cache) {
        // ** parameter validation
        ArgumentValidator::validate($id, ExtendsValidatorRule::getRule("Id"), true);
        ArgumentValidator::validate($displayName, StringValidatorRule::getRule(), true);
        ArgumentValidator::validate($description, StringValidatorRule::getRule(), true);
        ArgumentValidator::validate($cache, ExtendsValidatorRule::getRule("HierarchyCache"), true);
        // ** end of parameter validation
    
        $this->_id =$id;
        $this->_displayName = $displayName;
        $this->_description = $description;
        $this->_cache =$cache;
    }
 
    
    /**
     * Get the unique Id for this Hierarchy.
     *    
     * @return object Id 
     * 
     * @throws object HierarchyException An exception with one of
     *            the following messages defined in
     *            org.osid.hierarchy.HierarchyException may be thrown:     {@link }
     *            org.osid.hierarchy.HierarchyException#OPERATION_FAILED
     *            OPERATION_FAILED}, {@link }
     *            org.osid.hierarchy.HierarchyException#PERMISSION_DENIED
     *            PERMISSION_DENIED}, {@link }
     *            org.osid.hierarchy.HierarchyException#CONFIGURATION_ERROR
     *            CONFIGURATION_ERROR}, {@link }
     *            org.osid.hierarchy.HierarchyException#UNIMPLEMENTED
     *            UNIMPLEMENTED}
     * 
     * @access public
     */
    function getId () { 
        return $this->_id;
    }
 
    /**
     * Get the display name for this Hierarchy.
     *    
     * @return string 
     * 
     * @throws object HierarchyException An exception with one of
     *            the following messages defined in
     *            org.osid.hierarchy.HierarchyException may be thrown:     {@link }
     *            org.osid.hierarchy.HierarchyException#OPERATION_FAILED
     *            OPERATION_FAILED}, {@link }
     *            org.osid.hierarchy.HierarchyException#PERMISSION_DENIED
     *            PERMISSION_DENIED}, {@link }
     *            org.osid.hierarchy.HierarchyException#CONFIGURATION_ERROR
     *            CONFIGURATION_ERROR}, {@link }
     *            org.osid.hierarchy.HierarchyException#UNIMPLEMENTED
     *            UNIMPLEMENTED}
     * 
     * @access public
     */
    function getDisplayName () { 
        return $this->_displayName;
    }
    
    /**
     * Update the display name for this Hierarchy.
     * 
     * @param string $displayName 
     * 
     * @throws object HierarchyException An exception with one of
     *            the following messages defined in
     *            org.osid.hierarchy.HierarchyException may be thrown:     {@link }
     *            org.osid.hierarchy.HierarchyException#OPERATION_FAILED
     *            OPERATION_FAILED}, {@link }
     *            org.osid.hierarchy.HierarchyException#PERMISSION_DENIED
     *            PERMISSION_DENIED}, {@link }
     *            org.osid.hierarchy.HierarchyException#CONFIGURATION_ERROR
     *            CONFIGURATION_ERROR}, {@link }
     *            org.osid.hierarchy.HierarchyException#UNIMPLEMENTED
     *            UNIMPLEMENTED}
     * 
     * @access public
     */
    function updateDisplayName ( $displayName ) { 
        // ** parameter validation
        $stringRule = StringValidatorRule::getRule();
        ArgumentValidator::validate($displayName, $stringRule, true);
        // ** end of parameter validation
        
        if ($this->_displayName == $displayName)
            return; // nothing to update
        
        // update the object
        $this->_displayName = $displayName;
 
        // update the database
        $dbHandler = Services::getService("DatabaseManager");
        $db = $this->_cache->_hyDB.".";
        
        $query = new UpdateQuery();
        $query->setTable($db."hierarchy");
        $id =$this->getId();
        $idValue = $id->getIdString();
        $where = "{$db}hierarchy.hierarchy_id = '{$idValue}'";
        $query->setWhere($where);
        $query->setColumns(array("{$db}hierarchy.hierarchy_display_name"));
        $query->setValues(array("'".addslashes($displayName)."'"));
        
        $queryResult =$dbHandler->query($query, $this->_cache->_dbIndex);
        if ($queryResult->getNumberOfRows() == 0)
            throwError(new Error(HierarchyException::OPERATION_FAILED(),"Hierarchy",true));
        if ($queryResult->getNumberOfRows() > 1)
            throwError(new Error(HierarchyException::OPERATION_FAILED() ,"Hierarchy",true));
    }
 
    /**
     * Get the description for this Hierarchy.
     *    
     * @return string 
     * 
     * @throws object HierarchyException An exception with one of
     *            the following messages defined in
     *            org.osid.hierarchy.HierarchyException may be thrown:     {@link }
     *            org.osid.hierarchy.HierarchyException#OPERATION_FAILED
     *            OPERATION_FAILED}, {@link }
     *            org.osid.hierarchy.HierarchyException#PERMISSION_DENIED
     *            PERMISSION_DENIED}, {@link }
     *            org.osid.hierarchy.HierarchyException#CONFIGURATION_ERROR
     *            CONFIGURATION_ERROR}, {@link }
     *            org.osid.hierarchy.HierarchyException#UNIMPLEMENTED
     *            UNIMPLEMENTED}
     * 
     * @access public
     */
    function getDescription () { 
        return $this->_description;
    }
 
    /**
     * Update the description for this Hierarchy.
     * 
     * @param string $description 
     * 
     * @throws object HierarchyException An exception with one of
     *            the following messages defined in
     *            org.osid.hierarchy.HierarchyException may be thrown:     {@link }
     *            org.osid.hierarchy.HierarchyException#OPERATION_FAILED
     *            OPERATION_FAILED}, {@link }
     *            org.osid.hierarchy.HierarchyException#PERMISSION_DENIED
     *            PERMISSION_DENIED}, {@link }
     *            org.osid.hierarchy.HierarchyException#CONFIGURATION_ERROR
     *            CONFIGURATION_ERROR}, {@link }
     *            org.osid.hierarchy.HierarchyException#UNIMPLEMENTED
     *            UNIMPLEMENTED}, {@link }
     *            org.osid.hierarchy.HierarchyException#NULL_ARGUMENT
     *            NULL_ARGUMENT}
     * 
     * @access public
     */
    function updateDescription ( $description ) { 
        // ** parameter validation
        ArgumentValidator::validate($description, StringValidatorRule::getRule(), true);
        // ** end of parameter validation
        
        if ($this->_description == $description)
            return; // nothing to update
 
        // update the object
        $this->_description = $description;
 
        // update the database
        $dbHandler = Services::getService("DatabaseManager");
        $db = $this->_cache->_hyDB.".";
        
        $query = new UpdateQuery();
        $query->setTable($db."hierarchy");
        $id =$this->getId();
        $idValue = $id->getIdString();
        $where = "{$db}hierarchy.hierarchy_id = '{$idValue}'";
        $query->setWhere($where);
        $query->setColumns(array("{$db}hierarchy.hierarchy_description"));
        $query->setValues(array("'".addslashes($description)."'"));
        
        $queryResult =$dbHandler->query($query, $this->_cache->_dbIndex);
        if ($queryResult->getNumberOfRows() == 0)
            throwError(new Error(HierarchyException::OPERATION_FAILED(),"Hierarchy",true));
        if ($queryResult->getNumberOfRows() > 1)
            throwError(new Error(HierarchyException::OPERATION_FAILED(),"Hierarchy",true));
    }
    
    /**
     * Create a root Node. The Node is created with the specified unique Id,
     * and, unlike Nodes created with createNode, initially has no parents or
     * children.
     * 
     * @param object Id $nodeId 
     * @param object Type $nodeType 
     * @param string $displayName 
     * @param string $description 
     *    
     * @return object Node 
     * 
     * @throws object HierarchyException An exception with one of
     *            the following messages defined in
     *            org.osid.hierarchy.HierarchyException may be thrown:     {@link }
     *            org.osid.hierarchy.HierarchyException#OPERATION_FAILED
     *            OPERATION_FAILED}, {@link }
     *            org.osid.hierarchy.HierarchyException#PERMISSION_DENIED
     *            PERMISSION_DENIED}, {@link }
     *            org.osid.hierarchy.HierarchyException#CONFIGURATION_ERROR
     *            CONFIGURATION_ERROR}, {@link }
     *            org.osid.hierarchy.HierarchyException#UNIMPLEMENTED
     *            UNIMPLEMENTED}{@link }
     *            org.osid.hierarchy.HierarchyException#NULL_ARGUMENT
     *            NULL_ARGUMENT}, {@link }
     *            org.osid.hierarchy.HierarchyException#SINGLE_PARENT_HIERARCHY
     *            SINGLE_PARENT_HIERARCHY}
     * 
     * @access public
     */
    function createRootNode ( $nodeId, $nodeType, $displayName, $description ) { 
        // ** parameter validation
        ArgumentValidator::validate($nodeId, ExtendsValidatorRule::getRule("Id"), true);
        ArgumentValidator::validate($nodeType, ExtendsValidatorRule::getRule("Type"), true);
        ArgumentValidator::validate($displayName, StringValidatorRule::getRule(), true);
        ArgumentValidator::validate($description, StringValidatorRule::getRule(), true);
        // ** end of parameter validation
 
        return $this->_cache->createRootNode($nodeId, $nodeType, $displayName, $description);
    }
 
    /**
     * Create a Node. The Node is created with the specified unique Id and
     * initially has only the specified parent.
     * 
     * @param object Id $nodeId 
     * @param object Id $parentId 
     * @param object Type $type 
     * @param string $displayName 
     * @param string $description 
     *    
     * @return object Node 
     * 
     * @throws object HierarchyException An exception with one of
     *            the following messages defined in
     *            org.osid.hierarchy.HierarchyException may be thrown:     {@link }
     *            org.osid.hierarchy.HierarchyException#OPERATION_FAILED
     *            OPERATION_FAILED}, {@link }
     *            org.osid.hierarchy.HierarchyException#PERMISSION_DENIED
     *            PERMISSION_DENIED}, {@link }
     *            org.osid.hierarchy.HierarchyException#CONFIGURATION_ERROR
     *            CONFIGURATION_ERROR}, {@link }
     *            org.osid.hierarchy.HierarchyException#UNIMPLEMENTED
     *            UNIMPLEMENTED}, {@link }
     *            org.osid.hierarchy.HierarchyException#NULL_ARGUMENT
     *            NULL_ARGUMENT}, {@link }
     *            org.osid.hierarchy.HierarchyException#UNKNOWN_PARENT_NODE
     *            UNKNOWN_PARENT_NODE}, {@link }
     *            org.osid.hierarchy.HierarchyException#ATTEMPTED_RECURSION
     *            ATTEMPTED_RECURSION}
     * 
     * @access public
     */
    function createNode ( $nodeId, $parentId, $type, $displayName, $description ) { 
        // ** parameter validation
        ArgumentValidator::validate($nodeId, ExtendsValidatorRule::getRule("Id"), true);
        ArgumentValidator::validate($parentId, ExtendsValidatorRule::getRule("Id"), true);
        ArgumentValidator::validate($type, ExtendsValidatorRule::getRule("Type"), true);
        ArgumentValidator::validate($displayName, StringValidatorRule::getRule(), true);
        ArgumentValidator::validate($description, StringValidatorRule::getRule(), true);
        // ** end of parameter validation
 
        return $this->_cache->createNode($nodeId, $parentId, $type, $displayName, $description);
    }
 
    /**
     * Delete a Node by Id.     Only leaf Nodes can be deleted.
     * 
     * @param object Id $nodeId 
     * 
     * @throws object HierarchyException An exception with one of
     *            the following messages defined in
     *            org.osid.hierarchy.HierarchyException may be thrown:     {@link }
     *            org.osid.hierarchy.HierarchyException#OPERATION_FAILED
     *            OPERATION_FAILED}, {@link }
     *            org.osid.hierarchy.HierarchyException#PERMISSION_DENIED
     *            PERMISSION_DENIED}, {@link }
     *            org.osid.hierarchy.HierarchyException#CONFIGURATION_ERROR
     *            CONFIGURATION_ERROR}, {@link }
     *            org.osid.hierarchy.HierarchyException#UNIMPLEMENTED
     *            UNIMPLEMENTED}, {@link }
     *            org.osid.hierarchy.HierarchyException#NULL_ARGUMENT
     *            NULL_ARGUMENT}, {@link }
     *            org.osid.hierarchy.HierarchyException#NODE_TYPE_NOT_FOUND
     *            NODE_TYPE_NOT_FOUND}, {@link }
     *            org.osid.hierarchy.HierarchyException#INCONSISTENT_STATE
     *            INCONSISTENT_STATE}
     * 
     * @access public
     */
    function deleteNode ( $nodeId ) { 
        // ** parameter validation
        ArgumentValidator::validate($nodeId, ExtendsValidatorRule::getRule("Id"), true);
        // ** end of parameter validation
        
        $this->_cache->deleteNode($nodeId->getIdString());
    }
 
    /**
     * Add a NodeType to this Hierarchy.
     * 
     * @param object Type $type 
     * 
     * @throws object HierarchyException An exception with one of
     *            the following messages defined in
     *            org.osid.hierarchy.HierarchyException may be thrown:     {@link }
     *            org.osid.hierarchy.HierarchyException#OPERATION_FAILED
     *            OPERATION_FAILED}, {@link }
     *            org.osid.hierarchy.HierarchyException#PERMISSION_DENIED
     *            PERMISSION_DENIED}, {@link }
     *            org.osid.hierarchy.HierarchyException#CONFIGURATION_ERROR
     *            CONFIGURATION_ERROR}, {@link }
     *            org.osid.hierarchy.HierarchyException#UNIMPLEMENTED
     *            UNIMPLEMENTED}, {@link }
     *            org.osid.hierarchy.HierarchyException#NULL_ARGUMENT
     *            NULL_ARGUMENT}, {@link }
     *            org.osid.hierarchy.HierarchyException#ALREADY_ADDED
     *            ALREADY_ADDED}
     * 
     * @access public
     */
    function addNodeType ( $type ) { 
        throwError(new Error(HierarchyException::UNIMPLEMENTED(), "Hierarchy", true));
    }
 
    /**
     * Remove a NodeType from this Hierarchy.  Note that no Nodes can have this
     * NodeType.
     * 
     * @param object Type $type 
     * 
     * @throws object HierarchyException An exception with one of
     *            the following messages defined in
     *            org.osid.hierarchy.HierarchyException may be thrown:     {@link }
     *            org.osid.hierarchy.HierarchyException#OPERATION_FAILED
     *            OPERATION_FAILED}, {@link }
     *            org.osid.hierarchy.HierarchyException#PERMISSION_DENIED
     *            PERMISSION_DENIED}, {@link }
     *            org.osid.hierarchy.HierarchyException#CONFIGURATION_ERROR
     *            CONFIGURATION_ERROR}, {@link }
     *            org.osid.hierarchy.HierarchyException#UNIMPLEMENTED
     *            UNIMPLEMENTED}, {@link }
     *            org.osid.hierarchy.HierarchyException#NULL_ARGUMENT
     *            NULL_ARGUMENT}, {@link }
     *            org.osid.hierarchy.HierarchyException#NODE_TYPE_IN_USE
     *            NODE_TYPE_IN_USE}, {@link }
     *            org.osid.hierarchy.HierarchyException#NODE_TYPE_NOT_FOUND
     *            NODE_TYPE_NOT_FOUND}
     * 
     * @access public
     */
    function removeNodeType ( $type ) { 
        throwError(new Error(HierarchyException::UNIMPLEMENTED(), "Hierarchy", true));
    }
 
    /**
     * Get all the Nodes in this Hierarchy.
     *    
     * @return object NodeIterator 
     * 
     * @throws object HierarchyException An exception with one of
     *            the following messages defined in
     *            org.osid.hierarchy.HierarchyException may be thrown:     {@link }
     *            org.osid.hierarchy.HierarchyException#OPERATION_FAILED
     *            OPERATION_FAILED}, {@link }
     *            org.osid.hierarchy.HierarchyException#PERMISSION_DENIED
     *            PERMISSION_DENIED}, {@link }
     *            org.osid.hierarchy.HierarchyException#CONFIGURATION_ERROR
     *            CONFIGURATION_ERROR}, {@link }
     *            org.osid.hierarchy.HierarchyException#UNIMPLEMENTED
     *            UNIMPLEMENTED}
     * 
     * @access public
     */
    function getAllNodes () { 
        // if all the nodes haven't been cached then do it
        $nodes =$this->_cache->getAllNodes();
 
        // create the iterator and return them
        $obj = new HarmoniNodeIterator($nodes);
        return $obj;
    }
 
    /**
     * Get the root Nodes in this Hierarchy.
     *    
     * @return object NodeIterator 
     * 
     * @throws object HierarchyException An exception with one of
     *            the following messages defined in
     *            org.osid.hierarchy.HierarchyException may be thrown:     {@link }
     *            org.osid.hierarchy.HierarchyException#OPERATION_FAILED
     *            OPERATION_FAILED}, {@link }
     *            org.osid.hierarchy.HierarchyException#PERMISSION_DENIED
     *            PERMISSION_DENIED}, {@link }
     *            org.osid.hierarchy.HierarchyException#CONFIGURATION_ERROR
     *            CONFIGURATION_ERROR}, {@link }
     *            org.osid.hierarchy.HierarchyException#UNIMPLEMENTED
     *            UNIMPLEMENTED}
     * 
     * @access public
     */
    function getRootNodes () { 
        // if all the nodes haven't been cached then do it
        $nodes =$this->_cache->getRootNodes();
 
        // create the iterator and return them
        $obj = new HarmoniNodeIterator($nodes);
        return $obj;
    }
 
    /**
     * Get a Node by unique Id.
     * 
     * @param object Id $nodeId 
     *    
     * @return object Node 
     * 
     * @throws object HierarchyException An exception with one of
     *            the following messages defined in
     *            org.osid.hierarchy.HierarchyException may be thrown:     {@link }
     *            org.osid.hierarchy.HierarchyException#OPERATION_FAILED
     *            OPERATION_FAILED}, {@link }
     *            org.osid.hierarchy.HierarchyException#PERMISSION_DENIED
     *            PERMISSION_DENIED}, {@link }
     *            org.osid.hierarchy.HierarchyException#CONFIGURATION_ERROR
     *            CONFIGURATION_ERROR}, {@link }
     *            org.osid.hierarchy.HierarchyException#UNIMPLEMENTED
     *            UNIMPLEMENTED}, {@link }
     *            org.osid.hierarchy.HierarchyException#NULL_ARGUMENT
     *            NULL_ARGUMENT}, {@link }
     *            org.osid.hierarchy.HierarchyException#NODE_TYPE_NOT_FOUND
     *            NODE_TYPE_NOT_FOUND}
     * 
     * @access public
     */
    function getNode ( $nodeId ) { 
        // ** parameter validation
        ArgumentValidator::validate($nodeId, ExtendsValidatorRule::getRule("Id"), true);
        // ** end of parameter validation
        
        $idValue = $nodeId->getIdString();
        $node = $this->_cache->getNode($idValue);
        
        return $node;
    }
    
    /**
     * Answer TRUE if the a node exists with the given Id
     *
     * WARNING: NOT in OSID
     * 
     * @param object Id $nodeId 
     *    
     * @return boolean 
     * 
     * @access public
     */
    function nodeExists ( $nodeId ) { 
        // ** parameter validation
        ArgumentValidator::validate($nodeId, ExtendsValidatorRule::getRule("Id"), true);
        // ** end of parameter validation
        
        $idValue = $nodeId->getIdString();
        return $this->_cache->nodeExists($idValue);
    }
 
    /**
     * Get all NodeTypes used in this Hierarchy.
     *    
     * @return object TypeIterator 
     * 
     * @throws object HierarchyException An exception with one of
     *            the following messages defined in
     *            org.osid.hierarchy.HierarchyException may be thrown:     {@link }
     *            org.osid.hierarchy.HierarchyException#OPERATION_FAILED
     *            OPERATION_FAILED}, {@link }
     *            org.osid.hierarchy.HierarchyException#PERMISSION_DENIED
     *            PERMISSION_DENIED}, {@link }
     *            org.osid.hierarchy.HierarchyException#CONFIGURATION_ERROR
     *            CONFIGURATION_ERROR}, {@link }
     *            org.osid.hierarchy.HierarchyException#UNIMPLEMENTED
     *            UNIMPLEMENTED}
     * 
     * @access public
     */
    function getNodeTypes () { 
        $dbHandler = Services::getService("DatabaseManager");
        $query = new SelectQuery();
        
        $db = $this->_cache->_hyDB.".";
        // set the tables
        $query->addTable($db."node");
        $joinc = $db."node.fk_type = ".$db."type.type_id";
        $query->addTable($db."type", INNER_JOIN, $joinc);
        $hierarchyIdValue = $this->_id->getIdString();
        $query->addWhere($db."node.fk_hierarchy = '{$hierarchyIdValue}'");
 
        // set the columns to select
        $query->setDistinct(true);
        $query->addColumn("type_id", "id", $db."type");
        $query->addColumn("type_domain", "domain", $db."type");
        $query->addColumn("type_authority", "authority", $db."type");
        $query->addColumn("type_keyword", "keyword", $db."type");
        $query->addColumn("type_description", "description", $db."type");
        $queryResult =$dbHandler->query($query, $this->_cache->_dbIndex);
 
        $types = array();
        while ($queryResult->hasMoreRows()) {
            // fetch current row
            $arr = $queryResult->getCurrentRow();
            
            // create type object
            $type = new HarmoniType($arr['domain'],$arr['authority'],$arr['keyword'],$arr['description']);
            
            // add it to array
            $types[] =$type;
 
            $queryResult->advanceRow();
        }
        $queryResult->free();
        
        $result = new HarmoniTypeIterator($types);
        return $result;
    }
    
    /**
     * Get the Nodes of the specified Type in this Hierarchy.
     *
     * WARNING: NOT IN OSID - This method is not in the OSIDs as of version 2.0.
     *
     * @param object Type $nodeType 
     * @return object NodeIterator    Iterators return a set, one at a time.    The
     *            Iterator's hasNext method returns true if there are additional
     *            objects available; false otherwise.    The Iterator's next method
     *            returns the next object.     The order of the objects returned by
     *            the Iterator is not guaranteed.
     *
     * @throws HierarchyException if there is a general failure.
     *
     * @todo Replace JavaDoc with PHPDoc
     */
    function getNodesByType( $nodeType ) {
        // if all the nodes haven't been cached then do it
        $where = "type_domain = '".addslashes($nodeType->getDomain())."'";
        $where .= " AND type_authority = '".addslashes($nodeType->getAuthority())."'";
        $where .= " AND type_keyword = '".addslashes($nodeType->getKeyword())."'";
        $nodes =$this->_cache->getNodesFromDB($where);
 
        // create the iterator and return them
        $iterator = new HarmoniNodeIterator($nodes);
        return $iterator;
    }
 
    /**
     * Returns true if multiple parents are allowed; false otherwise.
     *    
     * @return boolean 
     * 
     * @throws object HierarchyException An exception with one of
     *            the following messages defined in
     *            org.osid.hierarchy.HierarchyException may be thrown:     {@link }
     *            org.osid.hierarchy.HierarchyException#OPERATION_FAILED
     *            OPERATION_FAILED}, {@link }
     *            org.osid.hierarchy.HierarchyException#PERMISSION_DENIED
     *            PERMISSION_DENIED}, {@link }
     *            org.osid.hierarchy.HierarchyException#CONFIGURATION_ERROR
     *            CONFIGURATION_ERROR}, {@link }
     *            org.osid.hierarchy.HierarchyException#UNIMPLEMENTED
     *            UNIMPLEMENTED}
     * 
     * @access public
     */
    function allowsMultipleParents () { 
        return $this->_cache->_allowsMultipleParents;
    }
 
    /**
     * Returns true if recursion allowed; false otherwise.
     *    
     * @return boolean 
     * 
     * @throws object HierarchyException An exception with one of
     *            the following messages defined in
     *            org.osid.hierarchy.HierarchyException may be thrown:     {@link }
     *            org.osid.hierarchy.HierarchyException#OPERATION_FAILED
     *            OPERATION_FAILED}, {@link }
     *            org.osid.hierarchy.HierarchyException#PERMISSION_DENIED
     *            PERMISSION_DENIED}, {@link }
     *            org.osid.hierarchy.HierarchyException#CONFIGURATION_ERROR
     *            CONFIGURATION_ERROR}, {@link }
     *            org.osid.hierarchy.HierarchyException#UNIMPLEMENTED
     *            UNIMPLEMENTED}
     * 
     * @access public
     */
    function allowsRecursion () { 
        return false;
    }
 
    /**
     * Traverse a Hierarchy returning information about each Node encountered.
     * 
     * @param object Id $startId 
     * @param int $mode 
     * @param int $direction 
     * @param int $levels 
     *    
     * @return object TraversalInfoIterator 
     * 
     * @throws object HierarchyException An exception with one of
     *            the following messages defined in
     *            org.osid.hierarchy.HierarchyException may be thrown:     {@link }
     *            org.osid.hierarchy.HierarchyException#OPERATION_FAILED
     *            OPERATION_FAILED}, {@link }
     *            org.osid.hierarchy.HierarchyException#PERMISSION_DENIED
     *            PERMISSION_DENIED}, {@link }
     *            org.osid.hierarchy.HierarchyException#CONFIGURATION_ERROR
     *            CONFIGURATION_ERROR}, {@link }
     *            org.osid.hierarchy.HierarchyException#UNIMPLEMENTED
     *            UNIMPLEMENTED}, {@link }
     *            org.osid.hierarchy.HierarchyException#NODE_TYPE_NOT_FOUND
     *            NODE_TYPE_NOT_FOUND}, {@link }
     *            org.osid.hierarchy.HierarchyException#UNKNOWN_TRAVERSAL_MODE
     *            UNKNOWN_TRAVERSAL_MODE}, {@link }
     *            org.osid.hierarchy.HierarchyException#UNKNOWN_TRAVERSAL_DIRECTION
     *            UNKNOWN_TRAVERSAL_DIRECTION}
     * 
     * @access public
     */
    function traverse ( $startId, $mode, $direction, $levels ) { 
        // Check the arguments
        ArgumentValidator::validate($startId, ExtendsValidatorRule::getRule("Id"));
        ArgumentValidator::validate($mode, IntegerValidatorRule::getRule());
        ArgumentValidator::validate($direction, IntegerValidatorRule::getRule());
        ArgumentValidator::validate($levels, IntegerValidatorRule::getRule());
 
        if ($mode != Hierarchy::TRAVERSE_MODE_DEPTH_FIRST()) {
            // Only depth-first traversal is supported in the current implementation.
            throwError(new Error(HierarchyException::UNKNOWN_TRAVERSAL_DIRECTION(), "Hierarchy", true));
        }
 
        $down = ($direction == Hierarchy::TRAVERSE_DIRECTION_DOWN());
        $result = $this->_cache->traverse($startId, $down, $levels);
 
        return $result;
    }
    
    
    /**
     * Clears the cache.
     *
     * WARNING: NOT IN OSID
     *
     * @access public
     ***/
    function clearCache() {
        $this->_cache->clearCache();
    }
}
 
?>