diff --git a/models/classes/interface.ReadableResultStorage.php b/models/classes/interface.ReadableResultStorage.php
index <HASH>..<HASH> 100644
--- a/models/classes/interface.ReadableResultStorage.php
+++ b/models/classes/interface.ReadableResultStorage.php
@@ -53,6 +53,7 @@ interface taoResultServer_models_classes_ReadableResultStorage {
      */
     public function getVariables($callId);
     public function getVariable($callId, $variableIdentifier);
+    public function getVariableProperty($variableId, $property);
     public function getTestTaker($deliveryResultIdentifier);
     public function getDelivery($deliveryResultIdentifier);
add a method in readable interface to get a property of a variable