Text for images used as links

I would be pleased to receive comments on what I say at 
http://www.it.uc3m.es/vlc/wai/wcag20formal.html#imagelink :

WCAG 2.0 says:

     "When an image is used as the content of a link, specify a text 
alternative for the image. The text alternative should describe the 
function of the link."

I completely disagree!!! The link's title (attribute) is 
for that purpose. The image's alt is just for describing the image, not 
for describing the function of the link.

Example:

This example shows the difference between img/@alt and a/@title.

<a href="http://validator.w3.org/check/referer" title="Validate this 
page">
<img class="logow3c" 
src="http://validator.w3.org/images/vxhtml-basic10.gif"
alt="XHTML Basic 1.0 icon" /></a>

Vicente Luque Centeno
Dep. Ingeniería Telemática
Universidad Carlos III de Madrid
http://www.it.uc3m.es/vlc