Styling xref in HTML output

Hi,

Among other things, I use xref to link to certain special functions and
classes that are documented in our manual pages. These particular anchors
should be styled differently via the CSS sheet. But I can't seem to figure
out how to get generate a class att. in the HTML output. What I'd like to
do is something like:

<xref linkend="ref.foo" role="spec_func" xrefstyle="select: title"/>

yielding

<a href="foo.html" class="spec_func" title="foo()"><i>foo()</i></a>

which would enable me to emphasize the special role of these programming
elements in our documentation.

BTW: also when you do something like

<filename class="directory">/usr/local/bin</filename>, I'd expect an HTML
output like such as

<span class="directory">/usr/local/bin</span> to appear. This is
apparently not the case when I examine the HTML output. At least, that is
what I deduce when looking at

http://www.docbook.org/tdg/en/html/filename.html

In help is greatly appreciated.

Best, Mads