<?xml version="1.0" standalone="yes"?>
<svg xmlns="http://www.w3.org/Graphics/SVG/svg-19990412.dtd" width="4in" height="3in">
  <desc>This example uses the switch element to provide a 
  fallback graphical representation of an equation, if 
  MathML is not supported.
  </desc>
<!-- The <switch> element will process the first child element
       whose testing attributes evaluate to true.-->
  <switch>
<!-- Process the MathML if the system-required attribute
         evaluates to true (i.e., the user agent supports MathML
         embedded within SVG). -->
    <foreignobject system-required="http://www.w3.org/TR/REC-MathML-19980407" width="100" height="50">
<!-- MathML content goes here -->
    </foreignobject>
<!-- Else, process the following alternate SVG.
         Note that there are no testing attributes on the <g> element.
         If no testing attributes are provided, it is as if there
         were testing attributes and they evaluated to true.-->
    <g>
<!-- Draw a red rectangle with a text string on top. -->
      <rect style="fill: red"/>
      <text>Formula goes here</text>
    </g>
  </switch>
</svg>