I wonder, Ian, did you ever looked to Cache (www.intersystems.com) It is called Post-relational, this is because it also can understand SQL. But it is a kind of OO-database, I don't know if it has all the OO-particularities like (multiple)inheritence, or object as field of another object.
Anyway, a fully functional single user license is free for download. it is the choice of many large health-systembuilders in the Netherlands (Nictiz) and the USA. regards Bert
