I am trying to create specialized document classes that have unique propertysheets, methods, are CatalogAware and renderable via <dtml-var ...>. I have been able to successfully build a structured-text document class that meets these criteria, however, I am unable to build an HTML document class. If I try to use OFS:DTMLDocument or OFS:DTMLMethod as my base class, the ZInstance attempt throws a TypeError with a value of 'unsliceable object'. I have tried many variations on this theme and none were successful. I thought I had a handle on ZClasses but I am obviously missing something major. Note: not that this has anything to do with the above, but I can subclass OFS:File and OFS:Image with no problem. I am using Zope version 2.3.1 on a Win2K platform. Any hints, insight, direction, further-reading links would be greatly appreciated. Thanks in advance... Eric