If people preferred RDF they could of course use

as the image, and
PHP Code:
<a href="external.php?type=rdf" target="_blank"> <img src="$stylevar[imgdir_misc]/rdf.gif" width="36" height="14" border="0"></a>
as the code
or....
PHP Code:
<a href="external.php?type=rss" target="_blank"> <img src="$stylevar[imgdir_misc]/rss.gif" width="36" height="14" border="0"></a>
<a href="external.php?type=rdf" target="_blank"> <img src="$stylevar[imgdir_misc]/rdf.gif" width="36" height="14" border="0"></a>
for both.