openssh unix dev - May 2007 - Open SSH Server User accounts

Hi,

As part of our product requirement, want to make use of OpenSSH to support
SFTP, SSH-FTP.

Was wondering if OpenSSH Server supports creation of user accounts, without
actually creating a corresponding OS level user account?
Alternatively can OpenSSH server make use of other user registries such as
database based or LDAP based ?

Any help in this regard will be very much appreciated.

Thanks,
Atul Gohad.