public function canHandle($type, $namespace)
   {
      # no type; namespace must match
      if ($type === null) {
         if ($this->namespace === null || $namespace !== $this->namespace) {
            return false;
         }
      }
      else {
         if ($this->type !== $type) {
            return false;
         }
         else if ($namespace !== null && $this->namespace !== $namespace) {
            return false;
         }
         else if ($namespace === null && $this->namespace !== null) {
            return false;
         }
      }

      return true;
   }