Hi, I want to find if an object is an instance of OFS.DTMLDocument.DTMLDocument How can I do that in an external method ? It raises an error saying that OFS.DTMLDocument.DTMLDocument is not a class when I try with isinstance() I've searched isinstance on ZDP and Zope.org without luck except for an email message I haven't understood about extension classes. please could someone help me ? thanks in advance Jerome Alet