> > It seems too simple. What am I missing?
>
> Adding RDB$SCHEMA_NAME (to stay consistent) to RDB$RELATIONS

And to RDB$PROCEDURES, etc ...

What length do you propose for RDB$SCHEMA_NAME ?

> Adding something like RDB$SCHEMAS (RDB$SCHEMA_NAME VARCHAR(xx) NOT NULL PRIMARY KEY, CREATOR
> VARCHAR(31) DEFAULT CURRENT_USER)
>
> Comments?

As for me - this is necessary

Regards,
Vlad