restful: Child lov with parent prompt

I have 2 dimensions, Parent and Child. The list of values of the Child dimension contains a prompt on the parent. With restful, I want to the the list of values for the child dimension. I've created a webi document with a prompted filter on the Child dimension. So I have 2 prompts one the webi document, one from the Child dimension and one from the list of values of the child dimension.

A call GET http://srvbi4acc:6405/biprws/raylight/v1/documents/{documentID}/parameters/{parameterID} for the child prompt returns the expected xml:

where 0 is the id of the parent dimension

I then use the resful call PUT http://srvbi4acc:6405/biprws/raylight/v1/documents/{documentID}/parameters/{parameterID} to answer the parent and the child's lov.

When the prompt on the parent in the list of values is not optional, everything is fine but when the prompt is optional, I get the error :

Bad Request WSR 00102 - Illegal argument (Suspicious identifier(s): [0])

In both case, I use the input xml (with true or false value for optional attribute of parameter):

<parameters>

     <parameter optional="true|false">

          <id>0</id>

          <answer>

               <values><value id="10" >Parent 10</value></values>

          </answer>

     </parameter>

     <parameter>

          <id>1</id>

          <answer>

               <info><lov><query intervalId="0" intervalSize="10000" /></lov></info>

          </answer>

     </parameter>

</parameters>

If I use the refresh="true" attribute to the query tag, I don't get any value for the child lov only:

Any ideas?