1 <?xml version="1.0"?>

     2 <!-- Colon in ID attribute name -->

     3 <!DOCTYPE foo [

     4 <!ELEMENT foo ANY>

     5 <!ATTLIST foo id  ID #IMPLIED

     6               ref IDREF #IMPLIED>

     7 ]>

     8 <foo ref="a:b">

     9  <foo id="a:b"/>

    10 </foo>