Other Requirements

1. When the user makes a data entry mistake and an error dialog is shown, always put input focus into the data entry field where the error ocurred when the error dialog is discarded
2. Usernames are unique in the database
   1. For instance, the user "Kim" can only be in the database once
3. Usernames and passwords are not case sensitive
   1. Example: There is no difference between the usernames "Kim" and "KIM"
4. A user cannot be named "UNKNOWN USER"