document popolo data model

Pages to document how to use the data model by using some common examples.

Also a tutorial on using the API and a page listing some of the client libraries available.
partly → party

I fin this paragraph quite hard to follow — I suspect it would be largely impenetrable for someone looking at this with no understanding already. I think an example here showing a Membership (and/or Post) without a Role, and then with one, could get the idea across well. In general, for a document like this (as opposed to a reference guide) the key issue is showing *why* you would or wouldn't use something, beyond just what it is.