I'm trying to embed the following SVG into my XSL-FO and run it thru FOP.
Although the SVG looks fine using Adobe's SVG viewer, I get a black circle
from FOP in the CVS version.  Apparently, it doesn't like the url() reference 
to the <radialGradient>.

<svg width="3.5in" height="1in" viewBox="0 0 680 200"
xmlns="http://www.w3.org/2000/svg" preserveAspectRatio="none">
 <g>
  <defs>
   <radialGradient id="PurpleToWhite" gradientUnits="objectBoundingBox"
cx=".5" cy=".5" r=".5">
    <stop offset="5%" stop-color="white"/>
    <stop offset="100%" stop-color="rgb(100,0,100)"/>
   </radialGradient>
  </defs>
  <rect fill="black" stroke="black" x="0" y="0" width="680" height="200"/>
  <circle r="80" cx="270" cy="100" fill="url(#PurpleToWhite)"/>
  <text font-family="Times" font-size="135pt" x="213" y="160"
fill="white">D</text>
 </g>
</svg>