1. ITEC 3220A Using and Designing Database Systems
Instructor: Prof Z. Yang
Course Website:
Office: DB 3049

2. Object-Oriented Database

3. Object Orientation Object Orientation OO Contribution areas
Set of design and development principles
Based on autonomous computer structures known as objects
OO Contribution areas
Programming Languages
Graphical User Interfaces
Databases
Design
Operating Systems

4. OO Concepts: Objects Abstract representation of a real-world entity
Unique identity
Embedded properties
Ability to interact with other objects and self
OID
Unique to that object
Assigned by system at moment of object’s creation
Cannot be changed under any circumstances
Can be deleted only if the object is deleted
Can never be reused

5. Attributes (Instance Variables)
Known as instance variables in OO environment
Domain:
Logically groups and describes the set of all possible values that an attribute can have

6. Object State
Set of values that object’s attributes have at a given time
Can vary, although its OID remains the same
To change the object’s state, change the values of the object’s attributes
To change the object’s attribute values, send a message to the object
Message will invoke a method

7. Messages and Methods Method:
Code that performs a specific operation on object’s data
Protects data from direct and unauthorized access by other objects
Used to change the object’s attribute values or to return the value of selected object attributes
Represent real-world actions

8. Classes
Collection of similar objects with shared structure (attributes) and behavior (methods)
Class instance or object instance
Each object in a class

9. Object Characteristics

10. Class Hierarchy
Superclass
Subclass
Class lattice

11. Inheritance
Ability of object to inherit the data structure and behavior of classes above it
Single inheritance
Class has one immediate superclass

12. Inheritance (Cont’d.) Multiple
Class has more than one immediate superclass

13. Abstract Data Types (ADT)
Describes a set of similar objects
Differs from conventional data types
Operations are user-defined
Uses encapsulation
Definitions needed for creation
Name
Data representation
Abstract data type operations and constraints

14. Object Classification
Simple
Only single-valued attributes
No attributes refer to other object
Composite
At least one multivalued attribute
Compound
At least one attribute that references other object
Hybrid
Repeating group of attributes
At least one refers to other object
Associative object

15. OO vs. E-R Model Components

16. Class-Subclass Relationship

17. Interobject Relationships
Attribute-Class Link
Object’s attribute references another object
Relationship Representation
Related classes enclosed in boxes
Double line on right side indicates mandatory
Connectivity indicated by labeling each box
1:1
1:M
M:N
M:N with an Intersection Class

18. 1:1 and 1:M Relationships

19. Employee-Dependent Relationship

20. Representing the M:N Relationship

21. Representing the M:N Relationship with Associated Attributes

22. Representing the M:N Relationship with Intersection Class

23. Late and Early Binding Late binding Early binding
Data type of attribute not known until runtime
Allows different instances of same class to contain different data types for same attribute
Early binding
Allows database to check data type at compilation or definition time

24. OODM vs. E-R Data Models Object, Entity, and Tuple
OODM object has behavior, inheritance, and encapsulation
OO modeling more natural
Class, Entity Set, and Table
Class allows description of data and behavior
Class allows abstract data types
Encapsulation and Inheritance
Object inherits properties of superclasses
Encapsulation hides data representation and method

25. OODM vs. E-R Data Models (Cont’d)
Object ID
Not supported in relational models
Relationships
OODM
Interclass references
Class hierarchy inheritance
Relational models
Value-based approach
Access
Relational models
SQL
OODM
Navigational
Set-oriented access

26. Example
Using the following ERD to create the equivalent OO representations.
User_ID
Item_ID
Checkout
USER
ITEM

27. More Example Assume the following business rules:
A course contains many sections, but each section has only one course
A section is taught by one professor, but each professor may teach one or more different sections of one or more course
A section may contain many students, and each student is enrolled in many sections, but each section belongs to a different course. (Students my take many courses, but they cannot take many sections of the same course.)
Each section is taught in one room, but each room may be used to teach several different sections of one or more courses
A professor advises many students, but a student has only one advisor

28. More Example (Cont’d)
Identify and describe the main classes of objects
Modify your description in part 1 to include the use of abstract types such as Name, DOB, and Address
Create the conceptual OO representations

29. More Example on OO Database
Using intersection class to represent the following relationship

30. OO Design Example
Design OO conceptual representations for an engineering company, using the following requirements:
A customer has a customer identifier. Other important attributes of each customer include name and address. They can request any number of work orders from the company.
The company maintains a list of materials. The data about materials include a material identifier, a name and cost.
A work order has a work order number, a creation date, a completion date, a work address and a set of (one or more) tasks. In addition, each work order has one optional supervising employee. Each employee has a number assigned by the company. Other important attributes of each employee include name and skill.
Each work order also has a collection of materials. The same material can be used by any number of work orders. Material requirement includes material quantity.
Each task has a task identifier, a task name, an hourly rate and estimated hours. Tasks are standardized across work orders so that the same task may be performed on many work orders. We have to keep record of actual hours of each task on a work order.

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