Hi Pablo,
I've uploaded what could be the next version of the web desktop you saw on our mashups page.
https://openacs.org/storage/view/ajax-portal.tar.gz
Take a look at lib/portalelement.adp and lib/portalement.tcl. You will see a switch. Case 2 will show you how we grab the xowiki content.
The code is originally by Deds Castillo which I think he derived from Gustaf's portlet code in xowiki.
I hope this helps.
Hamilton