Johan Carlsson wrote:

Hi, Reading up on ZPatterns I'm still confused about some thing's (sometimes more, sometimes less).

I wonder: When to use Rack, Folders w/Customize, attribute provider, sheetproviders etc.

In which solution do I get ZODB dependens.

Folder w/ Customizer support. When you use this, the DataSkin instances appear in the ZODB, and look like normal ZClass (or whatever) instances.

One important aspect for some of my applications are to be as "virtual" as possible.

Use Specialists. Specialists contain Racks. Each Rack manages a particular class of objects. You can store objects in the ZODB inside the Rack, or alternamtively, you can get the data from external sources. You can also combine both kinds of data to provide the attributes for a single object. I've just completed a fairly complex ZPatterns project, designed broadly according to Coad / ZPatterns / wisdom from PJE . I used both approaches, and, based on that experience, I suggest you use the Specialists approach unless you have a pressing need to have your dataskin instances "rooted" in the ZODB. In the latter case only, use Folder w/ Customizer support. Other the other hand, if you want to design a "normal" Zope application, but just get the flexibility of using Attribute Providers and Skinscript to coordinate your dataskin instances, then use Folder w/ Customizer support. -- Steve Alexander Software Engineer Cat-Box limited http://www.cat-box.net