1. Lecture 9 Object-Oriented Analysis
COP 4331 – OOD&P
Lecture 9
Object-Oriented Analysis

2. Object-Oriented Analysis
Sample problem taken from Object-Oriented Modeling and Design by James Rumbaugh, et.al., Prentice Hall, 1991.
Automated Teller Machine

3. ATM Problem Statement
Design the software to support a computerized banking network including both human cashiers and automatic teller machines (ATMs) to be shared by a consortium of banks. Each bank provides its own computer to maintain its own accounts and processes transactions against them. Cashier stations are owned by individual banks and communicate directly with their own bank's computers. Human cashiers enter account and transaction data. Automatic teller machines communicate with a central computer which clears transactions with the appropriate banks.

4. ATM Problem Statement (cont.)
An automatic teller machine accepts a cash card, interacts with the user, communicates with the central system to carry out the transaction, dispense cash, and prints receipts. The system requires appropriate recordkeeping and security provisions. The system must handle concurrent access to the same account correctly. The banks will provide their own software for their own computers; you are to design the software for the ATMs and the network. The cost of the shared system will be apportioned to the banks according to the number of customers with cash cards.

5. Identifying Object Classes
Extract nouns from problem statement
Eliminate spurious classes
Candidate nouns
Software, Banking Network, Cashier, ATM, Consortium, Bank, Bank Computer, Account, Transaction, Cashier Station, Account Data, Transaction Data, Central Computer, Cash Card, User, Cash, Receipt, System, Recordkeeping Provision, Security Provision, Access, Cost, Customer

6. Identifying Object Classes.2
Characteristics of unnecessary or incorrect classes
Redundant
Irrelevant
Vague
Attributes
Operations
Roles
Implementation Constructs

7. Identifying Object Classes.3
Classes Eliminated
Vague: System, Recordkeeping Provision, Security Provision, Banking Network
Redundant: User
Irrelevant: Cost
Attribute: Account Data, Receipt, Cash, Transaction Data
Implementation: Access, Software

8. Identifying Object Classes.4
Remaining, Good Classes
Account, ATM, Bank, Bank Computer, Cash Card, Cashier, Cashier Station, Central Computer, Consortium, Customer, Transaction
Note: It is sometimes necessary to add classes based on domain knowledge that are not part of the problem statement

9. Identifying Associations
Associations often correspond to stative verbs or verb phrases including
Location
Directed actions
Communication
Ownership
Satisfaction of a condition

10. Identifying Associations.2
Candidate verb phrases
Banking network includes cashiers and ATMs
Consortium shares ATMs
Bank provides bank computer
Bank computer maintain accounts
Bank computer processes transaction against account
Bank owns cashier station
Cashier station communicates with bank computer
Cashier enters transaction for account

11. Identifying Associations.2
Candidate verb phrases (cont.)
ATMs communicate with bank computer
Central computer clears transaction with bank
ATM accepts cash card
ATM interacts with user
ATM dispenses cash
ATM prints receipt
System handles concurrent access
Banks provide software
Cost apportioned to banks

12. Identifying Associations.3
Implicit verb phrases
Consortium consists of banks
Bank holds account
Consortium owns central computer
System provides recordkeeping
System provides security
Customers have cash cards
Problem domain relationships
Cash card accesses accounts
Bank employs cashiers

13. Identifying Associations.4
Discard unnecessary or incorrect associations
Associations involving eliminated classes
Irrelevant or implementation associations
Actions
Derived associations
Ternary associations
Misnamed associations
Role names
Qualified associations
Seek missing associations

14. Identifying Associations.4
Associations involving eliminated classes
Costs, receipts, cash, system, software
Irrelevant or implementation associations
Concurrent access
Actions
Accepts cash card, Interacts with user
Ternary associations
Processes transaction against account
Derived associations
Misnamed associations
Role names
Qualified associations

15. Adding Attributes Attributes are properties But NOT other objects Name
Card code
Password
Cash on hand
Date-time
Balance …

16. Developing An Object Model
Draw rectangles for objects
Add associations
Add multiplicities
Revise for inheritance
Consider further revision for simplification and clarity

17. Use Case Diagram and Interaction Diagrams
Develop Use Case Diagram
Develop Example Interaction Diagram