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An example: WidgetML with namespaces

<widget xmlns="http://www.widget.org"
        xmlns:xhtml="http://www.w3.org/TR/xhtml1"
        type="gadget">
  <head size="medium"/>
  <big><subwidget ref="gizmo"/></big>
  <info>
     <xhtml:head>
      <xhtml:title>Description of gadget</xhtml:title>
    </xhtml:head>
    <xhtml:body>
      <xhtml:h1>Gadget</xhtml:h1>
      A gadget contains a big gizmo
    </xhtml:body>
   </info>
</widget>

Now the main part of WidgetML uses the default namespace which has the URI http://www.widget.org;
XHTML uses the namespace prefix xhtml which is assigned the URI http://www.w3.org/TR/xhtml1.