Set reference to a Lab Resource in a Request programmaticaly

Hi all -

I'm using the putArtifact method in the RQMRestClient class provided with the RQM REST Client code -
My goal is to do the following steps from my client code:
- create a Request
- fulfill the Request
- reserve a Lab Resource based on the request attributes -

I'm fine with these steps, and they work fine, but I have only a problem I'd like to address and solve.
Once I have identified the Lab Resource to be In the Request, I'm not able to set the reference to the lab resource in the Request.
I have noticed that the reference to the reserved Resource in a Request is in the <configuration> section, as for this example :

<ns2>
<identifier>request/RQ1</identifier>
<ns2>1</ns2>
<ns2>2011-03-16T23:00:00.000Z</ns2>
<ns2>2011-03-16T09:44:34.647Z</ns2>
<ns2>Request 1 </ns2>
-....................
<ns2>
{"Assets":{"AssetInstance":}}}}}]}},"theIdentifier":"_EASt8E-yEeC3cbH1m29F3w"}]}}
</ns2>
<ns2>
........

The Request object exposes a method setConfiguration, that accepts a String as parameter. so my idea is to use this method to set the reference to lab resource, but I don't know how to generate the string the method is expecting, since I do not have any way (at least for my knowledge) to get the "identifier" of the Lab Resource...

Anyone can explain me how to use it??

thanks in advance
*piero