Acronymns..

Can someone shed light on the "acronym" element in docbook?

1. Consider the following Docbook XML:
============================
<acronym>XML</acronym>

2. The HTML Output I get
===================
<span class="acronym">XML</span>

3. I would have guessed that it would have been better to output something 
like this in HTML:
================================================================
<acronym title="eXtended Markup Language">XML</acronym>



Questions:
1. Isn't the  <acronym> element to allow for HTML acronyms element?
2. If so, how do you specify the "title" attribute?

--
Rajal