[Z3-sqlos] Schema declaration for RelatedJoin

[Anders Bruun Olsen]

Hi,

I'm playing around with sqlos to get to know it better. I have worked a
little bit with sqlobject in the past and I am porting an old Zope2 app
I wrote (which uses MySQL to store data) to Zope3 with sqlos. In all
simplicity it is a database for books. I have defined a person class and
a book class along with there respective SQLObjectContainer classes. Now
I need to be able to associate a person with a book to define authors.
I do that by adding a RelatedJoin attribute to both classes.
But how do I specify this in my schema?
I have googled it and it seems that only a russian has written anything
on the internet with the words sqlos and relatedjoin in the same
sentence :). I couldn't understand the messages but the code seems to
suggest using List(value_type=Choice()). But Choice needs a vocabulary,
which for the person class would of course be BookContainer and
vice-versa for the book class. But not only are vocabularies quite a
difficult thing to understand, but in Web Component Development with
Zope 3, Philipp von Weitershausen writes that vocabularies have been
deprecated in favor of sources. I have taken a look at ISource but is it
just enough to declare that my SQLObjectContainers implement ISource?
And how do I correctly declare the source for Choice?

Am I even close here, or is there a much better way to handle this?

-- 
Anders
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