We used to have graphics that showed the database schema of the JPA examples.
I'll send some sketches to Jordan so the graphics team can clean them up.
Jordan created two illustrations, one for roster and the other for order. Both figures have been included in the 6.0.7 IPS package and are available online. See the fix for order here: http://docs.oracle.com/javaee/6/tutorial/doc/giqst.html and the fix for roster here: http://docs.oracle.com/javaee/6/tutorial/doc/giqsq.html.