+ Diagnose lack of default ctor if object used in relationship Got two questions on the mailing list about that in one week. Maybe always diagnose lack of public ctor? Maybe with a warning if no relationship? The no_ctor pragma like no_id? For now only diagnose (error) for pointed-to objects since that will lead to uncompilable generated code (as opposed to user code). Another option would be to add an option to warn about the lack of default ctor in all persistent classes.