Hi again Sorry to bother you again. I just want to make _one_ example work. But all I get is (after I tried to authenticate with my Zope-Login, which failed) (I got this HTML-Source): <H2>Site Error</H2> <P>An error was encountered while publishing this resource. </P> <P><STRONG>Unauthorized</STRONG></P> Sorry, a site error occurred.<p> <!-- Traceback (innermost last): File /usr/lib/zope/lib/python/ZPublisher/Publish.py, line 223, in publish_module File /usr/lib/zope/lib/python/ZPublisher/Publish.py, line 187, in publish File /usr/lib/zope/lib/python/ZPublisher/Publish.py, line 171, in publish File /usr/lib/zope/lib/python/ZPublisher/mapply.py, line 160, in mapply (Object: testdtmlmeth) File /usr/lib/zope/lib/python/ZPublisher/Publish.py, line 112, in call_object (Object: testdtmlmeth) File /usr/lib/zope/lib/python/OFS/DTMLMethod.py, line 189, in __call__ (Object: testdtmlmeth) File /usr/lib/zope/lib/python/DocumentTemplate/DT_String.py, line 540, in __call__ (Object: testdtmlmeth) File /usr/lib/zope/lib/python/DocumentTemplate/DT_Let.py, line 149, in render (Object: name="0") File /usr/lib/zope/lib/python/TreeDisplay/TreeTag.py, line 154, in render (Object: a tree tag) File /usr/lib/zope/lib/python/TreeDisplay/TreeTag.py, line 260, in tpRender (Object: ApplicationDefaultPermissions) File /usr/lib/zope/lib/python/TreeDisplay/TreeTag.py, line 336, in tpRenderTABLE (Object: ApplicationDefaultPermissions) Unauthorized: [0] Why do I have to authenticate anyway? So this is what I did (with the help from this list): I added DTMLMethod "testdtmlmeth" (inside the root folder): <dtml-var standard_html_header> <h2><dtml-var title_or_id> <dtml-var document_title></h2> <p> This is the <dtml-var document_id> Document in the <dtml-var title_and_id> Folder. </p> <dtml-comment> <dtml-tree> <dtml-var title_or_id> </dtml-tree> </dtml-comment> <dtml-let name="0"> <dtml-tree id=name branches_expr="child_lookup(parent=name)"> <b><dtml-var name></b> </dtml-tree> </dtml-let> <dtml-var standard_html_footer> Then, I added External Method "child_lookup": Id: child_lookup Module Name: child_lookup2 Function Name: child_lookup3 And a file called "child_lookup2.py" inside my Extensions dir (which is /var/lib/zope/Extensions/): class _dummy: __allow_access_to_unprotected_subobjects__=1 def __init__(self, name): self.name=name def child_lookup3(parent): c = [] for i in range(0,5): c.append(_dummy("%s.%d"%(parent, i))) return c