'Varchar', 'MarketValue' => 'Money', 'FoundationYear' => 'Year' ]; private static $has_one = [ 'CEO' => CEO::class, 'PreviousCEO' => CEO::class, 'Owner' => DataObject::class // polymorphic ]; private static $has_many = [ 'CurrentStaff' => Staff::class . '.CurrentCompany', 'PreviousStaff' => Staff::class . '.PreviousCompany' ]; }