[Zope] How do You guys manage integrity in Zope

[Max Møller Rasmussen]

i have made a few sites in Zope by now, and I often have problems with
integrity in the database.

Ie. with a structure like this:

    users
        user1
        user2
        user3
        ...

    articles
        article1
        article2
        article3

If I have an author field in "article1" that is the id of "author2" and I
then delete "author2" I get an error when trying to get the authors
properties like e-mail, name etc. 

Off course I can test to see if the author exists before trying to pull out
the data, but this seems like a messy way to do it.

How do the rest of you guys solve this problem? Is zPatterns nessecary?

regards Max M