1  <!DOCTYPE doc [
 2  <!ELEMENT doc (isid*)>
 3  <!ELEMENT isid EMPTY>
 4  <!ATTLIST isid myid ID #IMPLIED>
 5  ]>
 6  <doc>
 7  <isid myid="dup"/>
 8  <isid myid="foo"/>
 9  <isid myid="bar"/>
10  </doc>