i want o create an ontology that would enable me to mange the users and grant specific rights to them based on their role.Suppose, i have a main node called Users, within the main node, i have sub-nodes like Administrator, Analyst,Normal User,Executive etc. to each of these sub-nodes, i want to grant specific rights  like Administrator can maintain records and publish them whereas a Normal User can only view the records and nothing else...on a similar fashion i would like to grant particular privileges.at the same time,tomorrow if i want to add a new type of user,i should be able to do that easily.
Kindly throw some light on this topic.i really need it . i would be really grateful if u could add code snippets as well...
anticipating an early response .
thank you!