Querying child data objects in AIF document services

i'm working on a PHP project that communicates with Dynamics AX 2009 over SOAP. I ran in to this problem where i want to query for an item with a specific 'itembarcode', but i cannot figure out how to reach the itembarcode field since it is a field within the child data object of 'InventItemBarcode_1' as you can see in this XML document:

  <InventDimCombination class="entity">
           <_DocumentHash>f2b444b4f78f086ef95c1b1fe92161fe</_DocumentHash>
           <AutoCreated>Yes</AutoCreated>
           <InventColorId>202</InventColorId>
           <InventDimId>00000043_074</InventDimId>
           <InventSizeId>6512</InventSizeId>
           <ItemId>ABBY</ItemId>
           <Name>ENDED</Name>
           <RecId>5637145084</RecId>
           <RecVersion>1105761997</RecVersion>
           <SCAWebOnline>No</SCAWebOnline>
           <SCAWebStatus>Inactive</SCAWebStatus>
           <SCAWebVisibility>Public</SCAWebVisibility>
           <InventItemBarcode_1 class="entity">
              <BarcodeSetupId>Standard</BarcodeSetupId>
              <InventDimId>00000043_074</InventDimId>
              <ItemBarcode>5711029000098</ItemBarcode>
              <ItemId>ABBY</ItemId>
              <RecId>5637144584</RecId>
              <RecVersion>1</RecVersion>
              <UseForInput>No</UseForInput>
              <UseForPrinting>No</UseForPrinting>
           </InventItemBarcode_1>

I can run queries like this where i ask for the parents fields (such as name, itemId etc) with success:

<ser:InventDimCombinationServiceFindRequest>
     <!--Optional:-->
     <quer:QueryCriteria>
        <quer:CriteriaElement>
           <quer:DataSourceName>InventDimCombination</quer:DataSourceName>
           <quer:FieldName>InventDimId</quer:FieldName>
           <quer:Operator>Greater</quer:Operator>
           <quer:Value1>00000042_075</quer:Value1>
           <!--Optional:-->
           <quer:Value2>?</quer:Value2>
        </quer:CriteriaElement>
     </quer:QueryCriteria>
  </ser:InventDimCombinationServiceFindRequest>

Is it possible to run a query based on child data object fields such as barcode? I have tried changing the DataSourceName in the query to 'ItemBarcode_1' but without luck.

Thanks in advance!