(unknown charset) <use> symbol & XMLHttpRequest

Is it either possible or intended that XMLHttpRequest can return a  
reference to a local symbol?
attached one possible method that fails to work for me...

I've also tried <use> with symbols in the SVG returned without success.

cheers

Jonathan Chetwynd

printf("<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\"?>
<svg xmlns=\"http://www.w3.org/2000/svg\"
      xmlns:xlink=\"http://www.w3.org/1999/xlink\">
<a xlink:href='%s'><circle cx=\"75\" cy=\"75\" r=\"25\" fill=\"yellow 
\" />
<text x=\"130\" y=\"65\">%s</text></a>
</svg>",trim($this->link),htmlspecialchars(trim($this->title)));
			break;
}