Marcus Green has published an updated Relationship Diagram (ER) for Moodle 2.8 in the forums. This update includes additional relationships which were not previously included and has also included the field comments which are usually removed during the process.
You can get the full link and resources that accompany it on Marcus’s post to the forums: https://moodle.org/mod/forum/discuss.php?d=316771
Otherwise you can check it out here http://www.examulator.com/er/ or here http://www.examulator.com/er/components/index.html
