<!DOCTYPE doc [
<!ELEMENT doc (#PCDATA | ns:a | ns:b)*>
<!ATTLIST doc
          attr  CDATA #REQUIRED
          xmlns:ns CDATA #IMPLIED>
<!ELEMENT a EMPTY>
<!ELEMENT b (#PCDATA)>
]>
<ns:doc ns:attr="val" xmlns:ns="http://www.example.org/test/">
   <ns:a/>
   <ns:b>first line</ns:b>
   <ns:b>second line</ns:b>
</ns:doc>