16
You can have authors and moderators.
Authors can post articles but not publish them.
Moderators can post / publish and approve articles based on their priviliges for a certain topic.
If i understand you right the member group can approve?
Then these members can edit / publish / approve articles based on their priviliges for a certain topic.
You can always post your questions on the AMS support site
http://xoops.novasmarttechnology.com/Latest version is also 2.42