change the defult namespace

[apachexmlbeans]

With the xmlbeans I made a xml file,however the namespace is "n1 n2" and so on,
<ns:Execute language="en_US" version="1.0.0" xmlns:ns=http://www.swe.com/ow>
<ns1:Identifier xmlns:ns1="http://www.swe.net";>org</ns1:Identifier>
<ns:DataInputs>
     <ns:Input>
          <ns1:Identifier xmlns:ns1="http://www.swe.net";>inder 
inner</ns1:Identifier>
          <ns1:Title xmlns:ns1="http://www.swe.net";>title</ns1:Title>
     </ns:Input>
</ns:DataInputs>
</ns:Execute>
how to specify them? they should look like this:
<com:Executelanguage="en_US" version="1.0.0" xmlns:com=http://www.swe.com/ow>
<net:Identifier xmlns:net="http://www.swe.net";>org</net:Identifier>
<com:DataInputs>
     <com:Input>
          <net:Identifier xmlns:net="http://www.swe.net";>inder 
inner</net:Identifier>
          <net:Title xmlns:net="http://www.swe.net";>title</net:Title>
     </com:Input>
</com:DataInputs>
</com:Execute>
 
PS:
what is the difference between the add and set method?
take the above for example:
Execute.addNewInstance(IdentifierType id)
Execute.setIdentifier(CodeType id)