Constraints (How They Affect Populating The Database)

Below are the table creation statements that constitute my database.  I am having trouble entering the first tuples in the Employee table.  Employee inherits attributes from the superclass, "Person" by using the "under" statement of the Illustra DBMS.

Also, Administrator, Representitive and Cashier are subclasses of Employee (among others) that have foreign keys associated with them.  I couldn't enter data into the Employee table because of the constraint on Name. I'm guessing the error was related to the Administrator, Representitive and Cashier tables. If I start with the lowest subclass i.e. Administrator and try to add a tuple, I get the following error:

insert into Administrator values
('111-11-1111', 'Jill Smatt',
'101-101-1010', '1901-01-01','Northern',2500000,'5111');
X23C00:integrity constraint violation: Constraint Name _ON_INSERT_REFERENTIAL_IN
TEGRITY_FOR_00000054f3_barbacci_Employee_1_

The Illustra DBMS allows a value of Null in the foreign key
attribute.  Does this mean I have to enter Null in the tables that reference Administrator, Representitive and Cashier?

As I said, if I try starting with Employee, I have a constraint problem, if I start with Person, I don't know how to make the Person an Employee and Persons DON'T automatically become Employees.

Also, I don't want to restructure my tables to not have constraints and then add them, unless, this is CLEARLY the easier way.  Here are my tables:

-- XYZ Bus Company

create table Company       --Corprate Headquarters
(
  Branch_Name varchar(20)not null,  --Corp. name (xyz) included
  Employee_SSN char(11)not null,
  primary key(Branch_Name, Employee_SSN)
);

create table Person
(
  SSN char(11) not null,
  Name varchar(20) not null,
  Phone char(12),
  DOB date,
  primary key (SSN)
);

create table Branch_Offices
(
  Branch_Name varchar(20) not null,
  Address varchar(30),
  Corp_Office char(11),        --XYZ Company
  Secretary varchar(20),
  Manager varchar(20),
  Bus_No varchar(3),                
  primary key(Branch_Name),
  foreign key(Branch_Name) references Company(Branch_Name)
);

create table Passenger
(
  Ticket_No varchar (10)not null,
  Reserv_No varchar(10),
  primary key(Name, Ticket_No)
)under Person;

create table Employee
(
  Branch_Name varchar(20) not null,
  Salary decimal(10,2),
  primary key(SSN, Branch_Name),
  foreign key(Branch_Name) references Company(Branch_Name)
 )under Person;

create table Secretary
(
  Yrs_of_Work int,
  Office_Name char(10),
  primary key(Name, Branch_Name)
)under Employee;

create table Manager
(
  Bonus decimal(10,2),
  Hours decimal(3,1),
  primary key(Name, Branch_Name)
 )under Employee;


create table Cashier
(
  Ticket_No varchar(10) not null,  
  primary key(Name, Ticket_No)
)under Employee;


create table Officer under Employee;

create table Administrator
(
  Route_No varchar(10) not null,            
  primary key(Name, Route_No)
)under Officer;

create table Representative
(
  Reservation_No varchar (10) not null,      
  primary key(Name, Reservation_No)
)under Officer;

create table Driver
(
  Driver_No varchar(5) not null,  
  Trip_No varchar(10) not null,    
  primary key(Driver_No, Trip_No)
)under Employee;

create table Bus
(
  Bus_No varchar(3) not null,
  Branch_Name varchar(20) not null,
  No_of_Seats int,
  Trip_No varchar(10),
  primary key (Bus_No),
  foreign key(Branch_Name) references Branch_Offices(Branch_Name)
);

create table Reservation
(
  Reserv_No varchar(10)not null,
  Passenger char(11)not null,
  Trip_No varchar(10),
  Rep_Name varchar(20),
  primary key (Reserv_No, Passenger),
  foreign key (Passenger) references Passenger(SSN),
  foreign key (Rep_Name) references Representative(Name)
);


create table Route
(
  Route_No varchar(10) not null,
  Origin varchar (15) not null,
  Destination varchar(15) not null,
  Trip_No varchar(10) not null,
  Ticket_No varchar(10),
  Administrator varchar(20),
  primary key(Route_No),
  foreign key(Administrator) references Administrator(Name)
);

create table Trip
(
  Trip_No varchar(10) not null,
  Trip_Date date,
  Driver_No varchar(5),
  Route_No varchar(10),
  Ticket_No varchar(10),
  Reserv_No varchar(10),
  Bus_No varchar(3),
  primary key (Trip_No),
  foreign key(Bus_No) references Bus(Bus_No),
  foreign key(Driver_No, Trip_No) references Driver(Driver_No, Trip_No),
  foreign key(Route_No) references Route(Route_No),
  foreign key(Reserv_No) references Reservation(Reserv_No)
);

create table Ticket
(
  Ticket_No varchar(10) not null,
  Passenger varchar(20) not null,
  Cashier_Name varchar(20),
  Price decimal(10,2),
  Ticket_Date date,
  Trip_No varchar(10) not null,
  Route_No varchar(10) not null,
  primary key(Ticket_No, Passenger),
  foreign key(Passenger) references Passenger(Name),
  foreign key(Trip_No) references Trip(Trip_No),
  foreign key(Route_No) references Route(Route_No),
  foreign key(Cashier_Name, Ticket_No) references Cashier(Name, Ticket_No)
);

insert into Passenger values ('333-33-3333','Joe Shmoe', '101-303-3030', '1903-03-03','7111','6111');
insert into Reservation values ('6111','333-33-3333','8111', null);
insert into Route values ('5111', 'Pittsburgh PA', 'San Diego CA', '8111','7111',null);
insert into Ticket  values('7111','Joe Shmoe', null, 8500, '1998-11-19', '8111', '5111');
--insert into Passenger values ('333-33-3333','Joe Shmoe', '101-303-3030', '1903-03-03','7111','6111');
--insert into Reservation values ('6111','333-33-3333','8111', null);
select * from ml_tables('barbacci');
                                                       

The error I receive for trying to start with Employee looks like this:

insert into Employee values
('111-11-1111', 'Jill Smatt',
'101-101-1010', '1901-01-01','Northern',2500000);
X23C00:integrity constraint violation: Constraint Name _ON_INSERT_REFERENTIAL_IN
TEGRITY_FOR_00000054f3_barbacci_Employee_1_

I feel this is happening because the attribute 'Name' is a foreign key for three employee tables - from the Route table to Administrator, from Reservation to Representitive, from Ticket to Cashier.

Is this correct????  Any suggestions??