1. Seminar 3: Making Good Progress Programming Paradigms [The Paradigms - Group 2]

2. We will always use system analysis and design at the start of every software project.

4. No approaches were taught to derived

5. Knowing an good approach can build a robust system design.

6. Let us learn an approach to do system analysis and design 

7. What is Object-Oriented Analysis & Design? 7 Teacher Student An approach that models a system as a group of interacting objects.

8. New approach to analysis & design 8

9. CRC Approach 9

10. What is CRC? Class, Responsibility & Collaboration Discovering the real world objects is a system Mapping the collaboration among classes and their responsibilities

11. Why CRC? Uses brainstorming and role-playing to maximize advantages of group work

12. Basics of CRC approach

13. OO Characteristics 13

14. The things they do Their relationship to other classes

15. Back of the card is used list attributes and write class description The things they do Their relationship to other classes

16. 16

17. QuickCRC 17

18. CRC books 18

19. 19

20. CRC Card 1. Discovering Candidate Classes 1. Read Requirements Documents 2. Clarifying the Scope 2. Underline nouns and noun phrases. 3. Selecting Core Classes 3. Add them to candidate class list. 4. Brainstorm to find other potential classes.

21. The ATM System will interface with the customer through a display screen , numeric and special input keys, a bankcard reader, a deposit slot, and a receipt printer. Customer may make deposits, withdrawals and balance inquires using the ATM machine, but the update of accounts will be handled by an interface to the Accounts system. Customers will be assigned a PIN and clearance level by the security system which will be verified prior to transactions. We would allow customers to update routine information such as change of address or phone number using the ATM. 1.Discovering The Candidate Class List 1. Read Requirements Documents

22. The ATM System will interface with the customer through a display screen , numeric and special input keys, a bankcard reader, a deposit slot, and a receipt printer. Customer may make deposits, withdrawals and balance inquires using the ATM machine, but the update of accounts will be handled by an interface to the Accounts system. Customers will be assigned a PIN and clearance level by the security system which will be verified prior to transactions. We would allow customers to update routine information such as change of address or phone numberusing the ATM. 1. Discovering The Candidate Class List 2. Underline nouns and noun phrases.

24. Customer

25. Display screen

26. Numeric

27. Special input keys

28. Bankcard reader

29. Deposit slot

30. Receipt printer

31. Deposits

32. Withdrawals

33. Balance inquires

34. Accounts

35. PIN

36. Clearance level

37. Security system

38. Transactions

39. Change of address

41. 25 Q: How does the customer access the ATM? 1. Discovering The Candidate Class List 4. Brainstorm to find other potential classes.

42. 1.Discovering The Candidate Class List Candidate Class List

43. 27 CRC Card 1. Read Requirements Documents 1. Discovering Candidate Classes 2. Underline nouns and noun phrases. 2. Clarifying the Scope 3. Add them to candidate class list. 3. Selecting Core Classes 4. Brainstorm to find other potential classes.

44. Clarifying System Scope What is and what is not part of the system.

45. Clarifying System Scope 29 What is the scope of the ATM system? Questions Does it handle everything? banking application user interface interactions between them Does it.. updates accounting records? records and mediates the transaction activity? Other Possible questions

46. Clarifying System Scope

47. 31 Clarifying System Scope The sharper the system boundaries, the easier the evaluation of candidate class list.

48. 32 CRC Card 1. Read Requirements Documents 1. Discovering Candidate Classes 2. Underline nouns and noun phrases. 2. Clarifying the Scope 3. Add them to candidate class list. 3. Selecting Core Classes 4. Brainstorm to find other potential classes.

49. Sort Candidate Class List

50. Essential Classes for the application 4. Selecting Core Classes

51. Class that we are NOT able to categorize without knowing the system boundaries and definition 4. Selecting Core Classes To be Reviewed further for categorization

52. Classes that are outsidethe system scope Printer, ScreenSave, and Prompt. Related to the user interface subsystem But not to the core banking application 4. Selecting Core Classes

53. 37 3. Selecting Core Classes Eliminate Unnecessary Classes Architectural Design Issues 1. Identify hot spots 1. Remove ghost classes 2. Use appropriate design patterns 2. Combine synonyms 3. Take advantage of existing software frameworks 3. Distinguish attributes from classes

54. What are Hot Spots? A hot spot is a portion of the system that is likely to change from one system variant to another.

56. Interfaces and the relationships among components will become less prone to changes.Aid in designing components where changes is seldom necessary or constraint to a class

59. Identify hot spots Withdrawal handling is a hot spot. Initially supports the dispensing of cash; future may require update of cash cards. The classes that touch this hot spot include Account, Withdrawal, FundsAvailable, and BankCard.

60. Benefits of Hot Spots

61. 44 3. Selecting Core Classes Eliminate Unnecessary Classes Architectural Design Issues 1. Identify hot spots 1. Remove ghost classes 2. Use appropriate design patterns 2. Combine synonyms 3. Take advantage of existing software frameworks 3. Distinguish attributes from classes

62. Design Patterns A design pattern is a design structure that has been successfully used in a similar context “No Point Reinventing the Wheel” “Reuse and Adapt existing”

63. Design Patterns Pioneers have laid out the foundations There exist library of patterns Apply them to them to the CRC cards Speed up analysis Application of Design Patterns may result in new classes that are not found during brainstorming

64. “System Interaction Pattern" AuthorizeSystemInteraction

65. Example AuthorizeSystemInteraction Encapsulate Communication between ATM and the bank existing security system

66. Example of Patterns that can be considered Clients Servers Transactions Interacting Systems Interacting Devices Etc…

67. Some Good Pattern Books

68. 51 3. Selecting Core Classes Eliminate Unnecessary Classes Architectural Design Issues 1. Identify hot spots 1. Remove ghost classes 2. Use appropriate design patterns 2. Combine synonyms 3. Take advantage of existing software frameworks 3. Distinguish attributes from classes

69. Framework A collection of classes that captures the architecture and basic operation of an application system. Systems are created by extending the given classes to add the specialized behaviors.

70. Frameworks are "upside down libraries“. System control resides in framework code that calls "down" to user-supplied code. A blue print for the implementation Framework

71. Example in ATM 54 There are many papers on ATM that has been successfully built These framework can also be standards that existing ATM follows

72. Part of a Framework 55

73. 56 In the event where there is no available framework Use design patterns to aid the design and analysis part of the application

74. 57 3. Selecting Core Classes Eliminate Unnecessary Classes Architectural Design Issues 1. Identify hot spots 1. Remove ghost classes 2. Use appropriate design patterns 2. Combine synonyms 3. Take advantage of existing software frameworks 3. Distinguish attributes from classes

75. Remove ghost classes Classes that do not fit within the application Classes that are related entities but are outside the system.

76. Example Printer, and Keypad are relevant but outside the application.

77. 60 3. Selecting Core Classes Eliminate Unnecessary Classes Architectural Design Issues 1. Identify hot spots 1. Remove ghost classes 2. Use appropriate design patterns 2. Combine synonyms 3. Take advantage of existing software frameworks 3. Distinguish attributes from classes

78. Combine synonyms Use a common name for same items This situation may arise when different groups within an organization use different names to refer to the same thing.

79. Similarity BankCustomerand AccountHolder are probably synonyms. Adopt one of them or create a new name.

80. Situation based Balance and FundsAvailablemay or may not be different in concepts Example: A policy of disallowing withdrawals for some period after deposit of a check.

81. Caution! Be careful when the same word actually refers to different things! New core classes may be needed.

82. 65 3. Selecting Core Classes Eliminate Unnecessary Classes Architectural Design Issues 1. Identify hot spots 1. Remove ghost classes 2. Use appropriate design patterns 2. Combine synonyms 3. Take advantage of existing software frameworks 3. Distinguish attributes from classes

83. Distinguish attributes from classes Some candidate classes may turn out to represent information only! A candidate class may be an attribute if: It does not have any operations It does not change

86. 69 So what do we have so far?

87. Annotated Candidate Class List Critical Classes FinancialTransaction Account BalanceInquiry Withdrawal Deposit AuthorizeSystemInteraction BankCard Undecided Classes BankCustomer(ghost - integrated with AuthorizeSystemInteraction) PIN (attribute) SavingsAccount(attribute of Account) CheckingAccount(attribute of Account) ATM (ghost -> system name) FundsAvailable(attribute) Balance (attribute) AccountHolder(synonym)

88. Annotated Candidate Class List Irrelevant Items Transfer Receipt ReceiptPrinter Keypad Screen CashDispenser ScreenMessage Display Deposit EnvelopeFailure TimeOut KeyTransaction LogPrinter ScreenSaver Prompt Numeric Key Key

89. Thank you! End of Presentation