Transversing data based on access level

hey folks,
i am just a newbie in xml. wanted to know what can xml do and what is the limit of it? basically i m working on a CMS, now based on security privilliges of the user. the people will have access to some pages of a module. now suppose i have a index.php but the person doesn’t have access to index.php instead he have access only to orders.php, now i can’t expose my dir structure to a user. how can i in real time switch the pages data. that suppose the order.php is transversed into index.php. is there is a possibility of doing that in xml?