Distinguish text from markup

• A DocBook element

• <programlisting><![CDATA[<value> <double>28657</double> </value>]]></programlisting>

• The content is: <value> <double>28657</double> </value>

• This is the same: <programlisting>&lt;value&gt; &lt;double&gt;28657&lt;/double&gt; &lt;/value&gt;</programlisting>