Role Based Access Control in a Tree System

database database-design rbac

why reinventing the wheel? Why don't you implement the Role Based Access Control standard? http://csrc.nist.gov/groups/SNS/rbac/

There are implementations for all databases.

http://www.tonymarston.net/php-mysql/role-based-access-control.html

database database-design rbac

If this is not too late, have a look at this:

http://vita.codeplex.com/wikipage?title=guide_authorization