Hi all, I want to use Zope as the persistent storage for a big number of instances of a python class inherited from UserList and I ask advice to this list's wisdom on the best strategy to use. The class models structured contents (text) organized as a hierarchical tree a few level deep and obtained by parsing an input data stream. The class instances are about 200.000 (i.e. BTree Folders will be needed), but their max. size is small (couple of KB). The key of using Zope (apart from being Python and object oriented) is to leverage the use of ZCatalog. I see 2 alternatives: 1. Store them as XMLDocument instances (from XMLKit) and use ParsedXML and XMLTransform to build a search and display UI using XSLTs. 2. Store them using their native python structure and build from scratch a dtml search and display UI. Main advantage of 2. should be performance (no extra xml layer), but standard Zope objects don't seems (at least as far I Know) to permit an easy implementation of hierarchies of UserList-like properties and I would like to maintain a 1 object for each class instance approach. On the other hand, the xml approach seems natural because of the hierarchical nature of the class, but I am worried about performance issues due to the extra xml layer. Any advice or experience in implementing something like this (essentially a big single-object searchable storage) will be very helpful. Also, is there any problem on using Zope 2.6 instead of 2.5.1 (in principle better indexing, but all python work done so far is in 2.1.3 and I am worried about potential incompatibilities among BTree, XMLKit, ParsedXML, XMLTRansform and Zope 2.6). Thanks in advance, --Giuseppe Bonelli