My doubt is about protecting data.

Is it possible to use Acegi to verify if a principal has rights to see just some parts of a XML file.
For instace:
'myuser' can see just tags that start with 'A'
We have a original XML file:
<Root>
<After>Some data</After>
<Before> Some other Data </Before>
</Root>

And the filtering the rights, the user will se this data:
<Root>
<After>Some data</After>
</Root>