<?xml version=β€œ1.0” standalone=β€œyes”?> <smil>

<body>
  <!-- The SMIL <switch> element will process the
       first child element which tests true and skip
       past all others. -->
  <switch>
    <!-- The system-required attribute tests to see if
         the user agent supports SVG. If true, then
         render the file drawing.svg. -->
    <ref system-required="http://www.w3.org/Graphics/SVG/svg-19990412.dtd" 
         type="image/svg" src="drawing.svg" />
    <!-- Else, render the alternate image. -->
    <img src="alternate_image.jpg" />
  </switch>
</body>

</smil>