Slides on access control with SPARQL

Eric,
The slides you and Fatih presented at the Cambridge Gathering are were quite
interesting and relevant for many of us (
http://www.w3.org/2009/Talks/0504-swobjects-ep/acls).

Could you add some additional explanations for slides #10-17, since it's not
easy to glean the logical connections/dependencies between the various steps
(e.g., SPARQL -> policies -> rules -> access permissions). For examples,
slide 13 needs more commentary in order to see how the permissions get
applied to the requests coming from sparql and going through rules.

I know others out there have voiced their interest in this demonstration, so
providing a clear description of your approach would be timely.

cheers,
Eric