1<?xml version="1.0" standalone="yes"?>
2<smil>
3  <body>
4    <!-- The SMIL <switch> element will process the
5         first child element which tests true and skip
6         past all others. -->
7    <switch>
8
9      <!-- The system-required attribute tests to see if
10           the user agent supports SVG. If true, then
11           render the file drawing.svg. -->
12      <ref system-required="http://www.w3.org/Graphics/SVG/svg-19990412.dtd" 
13           type="image/svg" src="drawing.svg" />
14
15      <!-- Else, render the alternate image. -->
16      <img src="alternate_image.jpg" />
17    </switch>
18  </body>
19</smil>
20
21
22