This document discusses the design of an ATM simulator software project. It describes the iterative development process, including initial requirements, use case modeling, class modeling, and state diagrams. The first iteration focuses on a basic ATM engine and console interface that supports withdrawal and balance inquiry transactions without a graphical user interface or bank integration. Subsequent iterations will expand functionality and improve the user interface.

1. ATM Simulator

2. Software Life Cycle Elicit requirements describe use cases Create a specification Design structure (classes and their relations) behavior state Implement Deploy Maintain & Enhance What about testing and documentation ? Why aren't they listed as steps in the life cycle?

3. Unified Software Process Iterative and Incremental Perform multiple iterations Incrementally (in each iteration) add functionality Start with most important use cases or requirements

4. ATM Simulator Design and implement an ATM Simulator that simulates the functions of a real ATM. The ATM will support PIN authentication, balance inquiry, and withdrawal. If time permits, we will add deposit and transfers. Goals Practice software development methodology using UML, interfaces, and inheritance. Use O-O design to limit the complexity of implementation.

5. ATM user interface (sort of) Our Simulator will have more buttons than this.

6. ATM main menu (sort of) Our Simulator may have more menu options than this.

7. ATM Phase 1 Develop requirements for an ATM with withdrawal and balance inquiry. Implement a simple ATM engine and console interface. Determine what public methods ( interface ) are needed for an ATM U.I. Determine what services are needed from the Bank subsystem. For this phase, we will use a dummy Bank. It approves all requests.

8. ATM Use Case: withdraw (1) Description : Customer withdraws money from account Actors : Bank customer with ATM card Steps : 1. ATM machine displays greeting. 2. Customer inserts card. 3. ATM reads card and prompts customer for PIN. 4. Customer enters PIN. 5. ATM contacts Bank to verify customer's PIN. 6. Bank verifies PIN. 7. ATM prompts customer for transaction type. 8. Customer chooses withdraw.

9. ATM Use Case: withdraw (2) 9. ATM asks customer to enter amount to withdraw. 10. Customer enters amount. 11. ATM verifies it has bills to provide this amount. 12. ATM contacts Bank to verify customer can withdraw the requested amount. 13. Bank verifies withdraw and debits customer's acct. 14. ATM dispenses amount and prompts customer to take money. 15. Customer takes money.

10. ATM Use Case: withdraw (3) 16. ATM prints receipt and prompts customer to take it. 17. Customer take receipt. 18. ATM asks customer if he wants another transaction. 19. Customer selects "no" option. 20. ATM returns customer's card. 21. Customer takes card.

11. ATM Use Case: withdraw (4) Extensions and Alternatives : Scenario : step 3, ATM cannot read valid acct number from ATM card. 3a. ATM prints message describing problem. 3b. execute steps 20-21 of main course. Scenario : step 6. Bank indicates PIN is incorrect. 6a. if count of failed PIN attempts is < 3, goto step 3. Otherwise, execute steps 20-21 of main course. Scenario : step 11, customer's entry is not a number or ATM cannot dispense the requested amount. 11a. Display message describing problem. 11b. Return to step 9.

12. ATM Use Case: withdraw (5) Extensions and Alternatives : Scenario : at any time after authentication the customer presses CANCEL button. __a. Return customer's card and prompt him to take it. Extension : a customer may have more than one account. Enable customer to choose account for withdrawal. Issue : if customer presses CANCEL should ATM return card or return to option's menu? Issue : after 3 failed PIN attempts should ATM notify Bank for security reasons? I.e., temporarily lock-out this ATM card.

13. ATM Use Case: balance inquiry (1) Description : Customer inquires his account balance Actors : Bank customer with ATM card Steps : 1. ATM machine displays greeting. 2. Customer inserts card. 3. ATM reads card and prompts customer for PIN. 4. Customer enters PIN. 5. ATM contacts Bank to verify customer's PIN. 6. Bank verifies PIN. 7. ATM prompts customer for transaction type. 8. Customer chooses balance inquiry.

14. ATM Use Case: balance inquiry (2) To be completed.

15. ATM Use Case: deposit (1) Description : Customer deposits funds (cash or checks) in account using a deposit envelop Actors : Bank customer with ATM card and funds Steps : 1. ATM machine displays greeting. 2. Customer inserts card. 3. ATM reads card and prompts customer for PIN. 4. Customer enters PIN. 5. ATM contacts Bank to verify customer's PIN. 6. Bank verifies PIN. 7. ATM prompts customer for transaction type. 8. Customer chooses deposit.

16. ATM Use Case: deposit (2) To be completed.

17. Use Case Factoring and Diagram Factor out common behavior from the use cases. Steps 1 - 7 are the same in all use cases. Displaying menu and choosing an option is another common task. Draw a Use Case Diagram. Helpful for visually actors and components. Free UML editor: ArgoUML (argouml.tigris.org)

18. Specification Use cases help you identify what a system should do. A software specification document clarifies what the program should do. This is usually part of a software contract. Can be formal or informal, but must be written . Specification will help identify classes and responsibilities.

19. Structure: identify classes

20. Nouns in the requirements document. Source: Dietel & Dietel, Java, How to Program .

21. Modeling Classes UML class diagrams Allows suppression of class attributes and operations Called an elided diagram Solid line that connects two classes represents an association numbers near end of each line are multiplicity values

22. Class Diagram with Association Attributes and methods are omitted (&quot; elided &quot;) In early design phase, concentrate on identifying classes and responsibilities first. numbers near end of each line are multiplicity

23. Modeling Classes UML class diagrams Solid diamonds attached to association lines indicate a composition relationship Hollow diamonds indicate aggregation – a weaker form of composition

24. Class diagram for ATM U.I. Association and Composition Used when one object &quot;owns&quot; or controls another Solid diamonds indicate composition relationship: the ATM is composed of these parts; the parts do not exist without the whole (ATM) Source: Dietel & Dietel, Java, How to Program

25. Class diagram for ATM U.I. Association and Composition Hollow (open) diamonds indicate association relationship: the whole possesses these parts, but the parts can exist without the whole. Examples: a Stack has a LinkedList, a Mailbox has Messages LinkedList addFirst addLast addAfter removeFirst removeLast delete isEmpty Stack push pop isEmpty

26. D iagram for ATM with Withdrawal However, in our implementation we will separate UI from ATM functionality (deposit, withdraw, etc). Source: Dietel & Dietel, Java, How to Program

27. ATM with Separate User Interface Separate ATM user interface from the class(es) that provide ATM functionality. user interface is screen, keypad, card slot, money dispenser, etc. Create a Java interface to define public methods. <<interface>> ATMInterface displayMessage ATMsim deposit( ) withdraw( ) balanceInquiry( ) ATM UI atmUI: ATMInterface ATM( atmUI ) <<ATM Logic Engine>>

28. ATM with Separate User Interface Benefits of using an interface : you can change the actual user interface without changing any other parts of the system Example : a class implementing ATMInterface is responsible for displaying messages, accepting input from keypad, reading ATM card, returning ATM card, printing receipts, and dispensing cash for a GUI interface, we may decide to divide these responsibilities into separate classes one main class, called a Façade , acts as interface between ATM Engine and the various component classes.

29. ATM with Separate User Interface Separate ATM user interface from the class(es) that provide ATM functionality. user interface is screen, keypad, card slot, money dispenser, etc. Create a Java interface to define public methods. <<interface>> ATMInterface displayMessage ATM deposit( ) withdraw( ) balanceInquiry( ) ATM GUI atmUI: ATMInterface ATM( atmUI ) <<ATM Logic Engine>> Keypad Screen Card Slot

30. Identify Class Responsibilities What are the main responsibilities of each class? responsibilities are usually activities or actions if a class doesn't have any responsibilities, it can be eliminated Example : initially write a console-based U.I. Later we will write a GUI for ATM. multiple programmers can work on different parts of project simultaneously helps to limit complexity and enforce good design

31. Identifying Class Attributes Identifying attributes Look for descriptive nouns and phrases in the requirements document Eliminate some nouns: (1) redundant, (2) abstract, (3) describe instances, (4) outside the problem boundary (domain) Create attributes and assign them to classes

32. Possible Attributes for ATM System

33. First Iteration Ignore the Bank and Account components. No GUI interface. Design a basic ATM engine, ATM interface (Java interface), and console-based UI. Handle only a few transactions: withdraw, fast cash.

34. Design: use a state chart A state chart diagram can help understand behavior. Wait for an ATM user Transaction Loop Start error Fail < 3 times Verify ATM card Verify PIN Code Fail 3 times or Cancel End Session / Return ATM card [Invalid/unreadable card]

35. Transaction Loop UML state chart diagram for transaction loop Display Transactions Menu Deposit dialog Withdraw dialog Show Balance get deposit envelop error OK Transaction Loop END Exit OK OK verify input and available balance fail OK OK cancel cancel &quot;Deposit&quot; action &quot;Inquiry&quot; action &quot;Withdraw&quot; action

36. Second Iteration (due Tues 6/9/2005) implement the ATMInterface.java as a console interface. write an ATM simulator that does this: read ATM card and PIN display transaction menu handle withdraw, fast cash, and balance inquiry use the ATMInterface for all I/O Design a Transaction class to encapsulate transactions.