Before starting on this I tested several db schema design applications, looking for a replacement for ModelRight, which I'd used on Windows. Tried ModelRight under Wine, but no joy. Ended up settling on MySQL Workbench, which is not perfect, but pretty good.

Worked out a complete schema for the project, which Workbench can export as SVG, PDF and various other types of thing. It's also able to export SQL to build the db, but this fails due to a bug in the version of MySQL that we're running, apparently; it gacks on foreign key creation altogether, and even has trouble with creating indexes. I guess I'll have to hand-edit the SQL and work table-by-table in PHPMyAdmin. Curses.