/**
  * AccessTableData constructor
  *
  * @param Schema $schema Which schema to access
  * @param string $pid The page of which the data is for
  * @param int $ts Time at which the data should be read or written, 0 for now
  */
 public function __construct(Schema $schema, $pid, $ts = 0)
 {
     parent::__construct($schema, $pid, $ts);
     if ($this->schema->isLookup()) {
         throw new StructException('wrong schema type. use factory methods!');
     }
 }