[Zope] dtml-tree issue

[Vangelis Mihalopoulos]

Hello,

I want to use dtml-tree. I want to populate this tree using an external 
method that like this one:

getChildren(parent_id)  =>  [child, child, child, ......]

where "parent_id" is a string and each child is a node (python object).
My problem is what kind of object must each node be, in order for the 
dtml-tree to work properly...
The dtml-method is like this (example, hierarchy of links):

<dtml-tree id=LINK braches_expr="getChildren(LINK)">
  <a href="<dtml-var LINK>"><dtml-var TITLE></a>
</dtml-tree>

I tried a dictionary, but i cannot retrieve the "LINK" in the branches_expr.
I made a class in the External Method with attributes "LINK" and 
"TITLE", but i get unauthorized exceptions...


Thanks for any help,
Vangelis