1  <?xml version="1.0"?>
 2  <!DOCTYPE book [
 3  <!ELEMENT book (doc)*>
 4  <!ELEMENT doc (isid)*>
 5  <!ELEMENT isid EMPTY>
 6  <!ATTLIST isid myid ID #IMPLIED>
 7  ]>
 8  <book>
 9  <doc>
10  <isid myid="mine"/>
11  <isid myid="dup"/>
12  </doc>
13  <!-- including another XML document with IDs -->
14  <doc xml:base="../ents/ids.xml">
15  <isid myid="dup"/>
16  <isid myid="foo"/>
17  <isid myid="bar"/>
18  </doc>
19  </book>