Sorry to drop in like this. Feel free to ignore this, but:
It looks like you have a good start at a database design for this project. In spite of that you may want to consider using an outside object to relation database project. Where I work we wrote our own 00-rdb code for one project, but for our current project we are using: http://www.hibernate.org/ It has all kinds of features you probably won't get around to implementing yourself. It also has a nice interface to eclipse: http://hibernatesynch.sourceforge.net/
If you are interested in using hibernate, I have a set of configuration files for the gdm.
There are other good projects out there too.
Thanks for the pointer (and sorry for the belated reply).
Hibernate is one of the O/R tools that is on my short list, but I haven't been able to spend much time evaluating it.
The HibernateSync project on SourceForge is apparently abandoned. It looks like the author has decided to go proprietary and stop releasing sources. I can't tell if anyone has picked up the SourceForge sources.