Error on Remove operation in Assign

Question

I have a remove operation within an assign, that removes unused attributes from an element. The problem is (I think) that the element and the attributes are from different namespaces. The remove operation is as follows:
<bpelx:remove>
<bpelx:target variable="DDSRequest" part="vraagBericht" query="/ns3:vraagBericht/ns3:body/ns3:PRS/@ns4:sleutelVerzendend"/>
</bpelx:remove>
When executing my BPEL process, I receive the following error:
Assign Operation Misuse.
The selection result at list entry # 0 does not have a parent node; remove operation cannot be performed.
This is stupid, since if I assign a value in an attribute right next to it:
<copy>
<from expression='"F"'/>
<to variable="DDSRequest" part="vraagBericht" query="/ns3:vraagBericht/ns3:body/ns3:PRS/@ns4:soortEntiteit"/>
</copy>
this works fine....
How do I remove those unused attributes? Is there anyway to change the default behaviour of the Assign activity to leave out all unused elements/attributes, instead of putting them in as empty elements/attributes?

Answer 1

No I can't, since I don't have all parameters in a single XML document variable. And I can't define my own document through an XSD, because then JDeveloper complains if I try to create a variable with that XSD, that it's not being used in a partnerlink. For some stupid reason you can't create your own variables with an XSD that's not used for any partnerlinks.So I can't create a single simple document to transform into the format I need.
Unless you mean that I can transform the document 'into itself'?