<< Does this one also work with hsql? >>
I expect it will. All you need do is make a new configuration resource (similar to hsqldb) to test it. Configuration resources are in org.mmbase.storage.implementation.database.resources
See:
http://www.mmbase.org/download/builds/2003-08-22/mmdocs/backenddevelopers/storage/index.html
For the first basic documentation on the storage layer.
Gomez
