<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG April 1999//EN" "http://www.w3.org/Graphics/SVG/svg-19990412.dtd">
<svg width="4in" height="3in">
  <defs>
    <symbol id="Triangle" min-x="0" min-y="0" max-x="100" max-y="100" ref-x="0" ref-y="50">
      <path d="M 0 0 L 0 100 L 100 50 z"/>
    </symbol>
  </defs>
  <desc>An double-headed arrow example using markers

  </desc>
  <path d="M0 0">
<!-- Place an arrowhead rotated 180 degrees at the 

         beginning of the path -->
    <marker href="#Triangle" width="200" height="200" style="text-transform: rotate(180)"/>
    <data d="M 2000 2000"/>
<!-- Turn off markers in the middle of the path -->
    <marker href=""/>
    <data d="L 4000 2000 L 4000 4000"/>
<!-- Place an arrowhead at the end of the path-->
    <marker href="#Triangle" width="200" height="200"/>
    <data d="L 6000 4000"/>
  </path>
</svg>
