[xwiki-devs] Create users/groups programmatically

Hi, I'm trying to create wiki users and groups programmatically. The problem arises in integration of XWiki with a portal solution. The users log in with the portal, the portal sets a cookie and the xwiki plugin for authentication picks it up. It checks if the user exists, if not creates it. So far so good. I can create a user with code mimicking the user creation code in XWiki.class. But I still have a problem grasping permissions. I'd like to add the user to a special group of portal users, which should be checked and created on the fly if need be. That group should have all the permissions needed. However I don't see a way of doing it. The xwiki.org documentation on the data model did not seem to cover this ground well. Can you give me some pointers? Thanks, J.L.Simon