I'm not really sure this is a problem but I have a feeling that it will bite me later on. Anyway.. I have defined a class that's both a container and has properties of its own. The class (it's a CMF class) derives from SkinnedFolder, PortalContent and DefaultDublinCoreImpl. The problem is that many of the attributes are only meaningful for the object itself, not for the contained objects. This doesn't really bother me, but I would like to avoid indexing (and putting in the metadata) these attributes. So, I cannot use attributes starting with _ to stop acquisition since this would preclude putting them in the index/metadata. I cannot use Aquisition.explicit since I have no control on the contained objects (in fact the purpose of having a class deriving on SkinnedFolder is to use existing types as content). I've tried, with no success, the following: class MyClass(SkinnedFolder, PortalContent, DefaultDublinCoreImpl): .... .... def MyAttr(self): if not isinstance(aq_base(self),MyClass): return None .... .... No success because when the method gets called self is an instance of MyClass, so the method never returns None. Any hint? TIA -- Luca Olivetti Wetron Automatización S.A. http://www.wetron.es/ Tel. +34 93 5883004 Fax +34 93 5883007