A link element may contain optional 
xlink:role and xlink:title 
attributes that describe the remote resource, that is, the 
document or other resource to which the link points
The title contains a short plain text description.
The role contains a URI pointing to a long description.
<AUTHOR 
 xmlns:xlink="http://www.w3.org/1999/xlink"
 xlink:href="mailto:elharo@metalab.unc.edu"
 xlink:title="Send email to Elliotte Rusty Harold" 
 xlink:role="http://www.macfaq.com/personal.html">
  Please drop me a line.
</AUTHOR>
As with all other attributes, the 
xlink:title and xlink:role 
attributes should be declared in the DTD for all the 
elements to which they belong. For example, this is a 
reasonable declaration for the above AUTHOR 
element:
<!ELEMENT AUTHOR (#PCDATA)>
<!ATTLIST AUTHOR
  xmlns:xlink CDATA #FIXED "http://www.w3.org/1999/xlink"
  xlink:type  CDATA #FIXED "simple"
  xlink:href  CDATA #REQUIRED
  xlink:title CDATA #IMPLIED
  xlink:role  CDATA #IMPLIED
>