<tst:root    xmlns:tst="http://testspace"
              xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

     <tst:node id="1" typeAAttrib="an attribute" xsi:type="tst:NodeA"/>
     <tst:node id="2" typeBAttrib="another attribute" xsi:type="tst:NodeB" />

</tst:root>