1. Subclasses and Superclasses
Explain the cohort of the subject. Everyone has different pre-knowledge about some of the aspects.
(Source: Elmasri and Navathe, Fundamentals of Database Systems, Figure 1, page 248)

2. Disjointed Constraint
EmpID
EmpID
EName
EName
EAddress
EMPLOYEE
EAddress
EMPLOYEE
EDob
EDob d o
TypingSpeed
TypingSpeed
EngType
SECRETARY
SECRETARY
ENGINEER
ENGINEER
EngType
TECHNICIAN
TECHNICIAN
TGrade
TGrade
An Employee, say with ID “001” is: a secretary, OR a technician OR an engineer.
An Employee, say with ID “001” is: a secretary, OR a technician OR an engineer OR combination of the subclasses entities.

3. Completeness Constraint
EmpID
EmpID
EName
EName
EAddress
EMPLOYEE
EAddress
EMPLOYEE
EDob
EDob d d
Salary
PayScale
Salary
PayScale
SALARIED
EMPLOYEE
HOURLY
EMPLOYEE
SALARIED
EMPLOYEE
HOURLY
EMPLOYEE
An Employee, say with ID “001” is: a salaried employee OR an hourly employee.
An Employee, say with ID “001” is: a salaried employee OR an hourly employee OR none of them.

4. Transformation of Specialization/Generalization
Option 8A: Multiple relations-Superclass and subclasses
Option 8B: Multiple relations-Subclass relations only
Option 8C: Single relation with one type attribute
Option 8D: Single relation with multiple type attributes
Disjointed
Completeness
Remarks
“d”
“o”
“p”
“t” 8A  8B * 
*Redundancy of values of superclass entity’s attributes in all subclasses tables. 8C
Can generate many NULL values if many local attributes exist in the subclasses entities. 8D
Explain the cohort of the subject. Everyone has different pre-knowledge about some of the aspects.
The selection of option is affected by variety of reasons, including the constraints of the relationships, the attributes of the entities and the cost to process the queries.

5. Specialization vs Union*
Is-a
SUB-CLASS
SUPER-CLASS
* See problem on the previous lecture.
Jaime (owns Veh. ABC)
Bank of Stark (owns Veh. DEF)
Cersei & Bank of Lannister (own Veh. XYZ)
Jaime (owns Veh. ABC)
Bank of Stark (owns Veh. DEF)
Cersei & Bank of Lannister (own Veh. XYZ) o
PERSON
BANK
OWNER
OWNER
BANK
PERSON U
Jaime, 40 y/o
Cersei, 40 y/o
Tyrion, 38 y/o
Bank of Lannister
Bank of Stark
Bank of Targaryen
Jaime, 40 y/o
Cersei, 40 y/o
Tyrion, 38 y/o
Bank of Lannister
Bank of Stark
Bank of Targaryen