Source of page_ex.xml
(The markup is highlighted in blue and the preamble in red.) 

<?xml version="1.0"?>
<!DOCTYPE page SYSTEM "page_ex.dtd">
<?xml-stylesheet type="text/xsl" href="page_ex.xsl"?>
<page name="page_ex.html"
 home="javascript:history.go(-1)"
 next="index.html"
 classification="Document"
 description="Example of an XML structured document"
 keywords="XML, document, structure"
>

  <title>Example of XML document converted to HTML</title>
  <sections>
    <section>
      <title>First section</title>
      <body>This is a simple example of page with two sections.
        In the second section also HTML elements are used to fine
        tune the presentation.
      </body>
    </section>
    <section>
      <title>Second section</title>
      <body>As a rule a page on this site corresponds to a document
        although not always contained within one window.
        <br/>The page element has a number of attributes:
        <ul>
        <li>home, next, previous (navigation control)</li>
        <li>classification, description, keywords (meta tags)</li>
        </ul>
      </body>
    </section>
  </sections>
</page>