Work out the class to instantiate a resource as @ignore
protected function classForResource($uri) {
  $resClass = 'EasyRdf_Resource';
  $rdfType = EasyRdf_Namespace::expand('rdf:type');
  if (isset($this->index[$uri][$rdfType])) {
    foreach ($this->index[$uri][$rdfType] as $type) {
      if ($type['type'] == 'uri' or $type['type'] == 'bnode') {
        $class = EasyRdf_TypeMapper::get($type['value']);
        if ($class != null) {
          $resClass = $class;
          break;
        }
      }
    }
  }
  return $resClass;
}