The owner can be any user known to the VOB server's operating system. The group must be one of the VOB's groups: either the VOB's primary group or one of its additional groups.
Because a VOB is managed by a process using the identity of the VOB owner and all the VOB groups, a VOB is limited in the number of additional groups—the limits of 16 (UNIX) or 32 (Windows) groups apply to the additional groups list.