Metacat

<?xml version="1.0"?>

<!DOCTYPE testroot [

  <!ELEMENT testroot (a)>

  <!ELEMENT a (b*,c*)>

  <!ATTLIST a testatt CDATA #REQUIRED>

  <!ELEMENT b (#PCDATA)>

  <!ELEMENT c (#PCDATA)>

  <!ATTLIST c newatt CDATA #IMPLIED>

]>

<testroot>

  <a testatt="attvalue1">

    <b>Value1</b>

    <c newatt="89766">Value2</c>

  </a>

</testroot>