lithium\data\source\MongoDb::relationship PHP Method

    public function relationship($class, $type, $name, array $config = array())
    {
        $fieldName = $this->relationFieldName($type, $name);
        $config += compact('name', 'type', 'key', 'fieldName');
        $config['from'] = $class;
        return $this->_instance('relationship', $config + array('strategy' => function ($rel) use($config, $class, $name, $type) {
            if (isset($config['key'])) {
                return array();
            }
            $link = null;
            $hasLink = isset($config['link']);
            $result = array();
            $to = $rel->to();
            $local = $class::key();
            $className = $class::meta('name');
            $keys = array(array($class, $name), array($class, Inflector::singularize($name)), array($to, Inflector::singularize($className)), array($to, $className));
            foreach ($keys as $map) {
                list($on, $key) = $map;
                $key = lcfirst(Inflector::camelize($key));
                if (!$on::hasField($key)) {
                    continue;
                }
                $join = $on === $class ? array($key => $on::key()) : array($local => $key);
                $result['key'] = $join;
                if (isset($config['link'])) {
                    return $result;
                }
                $fieldType = $on::schema()->type($key);
                if ($fieldType === 'id' || $fieldType === 'MongoId') {
                    $isArray = $on::schema()->is('array', $key);
                    $link = $isArray ? $rel::LINK_KEY_LIST : $rel::LINK_KEY;
                    break;
                }
            }
            if (!$link && !$hasLink) {
                $link = $type === "belongsTo" ? $rel::LINK_CONTAINED : $rel::LINK_EMBEDDED;
            }
            return $result + ($hasLink ? array() : compact('link'));
        }));
    }

 /**
  * Extended for full namesapce support
  */
 public function relationship($class, $type, $name, array $config = array())
 {
     if (isset($config['to'])) {
         $config['to'] = Libraries::locate('models', $config['to']);
     }
     return parent::relationship($class, $type, $name, $config);
 }