[Zope] Why can't this be done???

[Jochen Haeberle]

Hi,

please forgive my probabyl stupid questions... but I am doing my 
first steps in Zope and unfortunately, I do not
have an python background.

I am working on a Newssystem. Editors are going to publish articels, 
related materials and pictures and are
given the choice to add a poll and/or a discussion to their articel.

I wanted to include the main discussion page of ZDiscussion or the 
included ZDConfera on the page of the articel itself,
not just link to it. Therefore I created a folder for my articel, and 
put a ZDiscussion topic, named disc, inside.
In my article page, I tried

<dtml-with disc>
  <dtml-var index_html>
</dtml-with>

This gives a key error

even the most simplest form (although I doubt this should work correctly)

<dtml-var disc.index_html>

does return an error. Why is the ZDiscussion folder something 
special??? What's wron about my tries?
Is there a way to do what I want?

Jochen