<!DOCTYPE doc [
<!ATTLIST e2 xml:space (default|preserve) 'preserve'>
<!ATTLIST e3 id ID #IMPLIED>
]>
<doc xmlns="http://www.ietf.org" xmlns:w3c="http://www.w3.org" xml:base="http://www.example.com/something/else">
   <e1>
      <e2 xmlns="" xml:id="abc" xml:base="../bar/">
         <e3 id="E3" xml:base="foo"/>
      </e2>
   </e1>
</doc>