&lt;!DOCTYPE para PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
          "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd"&gt;
&lt;para&gt; 
All user-interface components must be descendants of the
&lt;classname&gt;Widget&lt;/classname&gt; class.
&lt;/para&gt;