Creating a forest of permissions in Joomla! 1.6
DISCLAIMER: This article discusses a theoretical technique for manipulating the Access Control Levels in Joomla! 1.6. This technique is not necessarily the designed behavior of Joomla! 1.6, has not been fully tested, and may result in undesirable behavior. Proceed with a wee bit of caution.
By default, Joomla! 1.6 has a single tree for managing user groups. This tree is based upon the group "public" of which all branches of groups, and sub-groups, belong to.
However, is is possible to create a new tree, trees, or even a forest for other user groups and sub-groups. To do this, one needs to create the trees via SQL with a query such as:
This query will plant a second tree by the name of Private. You can then create new groups, that belong to this tree, as you would normally do so. 
Although this technique offers the potential for great granularity in creating and organizing user groups, introducing new user trees can also greatly increase the complexity of your website's access control levels.
