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COSC3311 – Software Design

Learn about object-oriented software design strategies, requirements analysis, and development approaches. Explore case studies and essential readings on software quality and engineering. Develop a deep understanding of requirements to code processes.

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COSC3311 – Software Design

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  1. COSC3311 – Software Design Section P Vassilios Tzerpos Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM0

  2. Course Details • www.cs.yorku.ca/course/3311 • Slides and other resources:http://www.cs.yorku.ca/course/3311/sectionP/ • Case studies: http://www.cs.yorku.ca/course/3311/sectionM/ • Eiffel Help:www.cs.yorku.ca/eiffel • Office hours: WF 2:30 – 3:30 • Read newsgroup • Lab hours next week: • Monday, January 12 3-4 • Wednesday, January 14 3-4 • Friday, January 16 3-4 Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM1

  3. Grading • Assignment 1: 7% • Assignment 2: 10% • Assignment 3: 13% • Test: 25% • Exam: 45% Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM2

  4. Textbook • Bertrand Meyer: Object-Oriented Software Construction, 2nd edition. Prentice Hall, 1997. • Suggested reading: • Pete Thomas, Ray Weedon, Object-Oriented Programming in Eiffel, second edition, Addison-Wesley, 1998. • Kent Beck, Test-driven development : by example. Addison-Wesley, Boston, 2003. • J.M. Jezequel and C. Mingins. Design patterns and contracts. Addison-Wesley, 2000. • Erich Gamma et al.: Design Patterns. Addison-Wesley, 1995. Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM3

  5. Advice – Course strategy • Don’t fall behind: First two weeks especially! • Attend lectures: material is not all in textbook • Do the readings on time Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM4

  6. Week 1 – Readings • January 5 • Software Quality & Engineering -- The context for design; what is design; Eiffel programming; classes. • Readings Required: Chapter 7 • Static Structure • Classes • Class POINT … • Readings Background: Chapters 1, 2 • External Quality • Internal Quality – Modularity • Read about, install and use EiffelStudio Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM5

  7. The goal: Software quality • REUSABILITY • EXTENDIBILITY • RELIABILITY (Correctness + Robustness) • PORTABILITY • EFFICIENCY • … • Correctness: • The ability of a software system to perform according to specification, in cases defined by the specification. • Robustness: • The ability of a software system to react in a reasonable manner to cases not covered by the specification. SPECIFICATION Robustness Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM6

  8. Case Study 1– Bank example Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM7

  9. Requirements – Bank example • Requirements • Open an account for a customer (savings or chequing) • Deposit • Withdraw • Display details of an account • Change LOC • Produce monthly statements • Print a list of customers • … • Ambiguities • What is the difference between savings and chequing? • Many others … Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM8

  10. Case Study 1 – Bank example • How should we go from Requirements to Code? • Two basic approaches • Plan-driven (waterfall type models) • Agile(incremental approaches) Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM9

  11. Requirements to Code? Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM10

  12. The waterfall model of the lifecycle FEASIBILITY STUDY REQUIREMENTS ANALYSIS SPECIFICATION GLOBAL DESIGN DETAILED DESIGN IMPLEMENTATION VALIDATION & VERIFICATION DISTRIBUTION PROJECT PROGRESS Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM11

  13. Problems with the waterfall • Late appearance of actual code. • Lack of support for requirements change — and more generally for extendibility and reusability. • Lack of support for the maintenance activity (70% of software costs?). • Division of labor hampering Total Quality Management. • Impedance mismatches. • Highly synchronous model. Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM12

  14. Impedance mismatches As Management requested it. As the Project Leader defined it. As Systems designed it. As Programming developed it. As Operations installed it. What the user wanted. (Pre-1970 cartoon; origin unknown) Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM13

  15. How to think about requirements? • Use Cases Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM14

  16. System boundary Use Case Bank Requirements – Use Cases Actors Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM15

  17. Bank Use Cases • Challenge question: • What would the Use Case diagram look like if the bank supplies ATMs in addition to tellers? Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM16

  18. Use Case – Open Account • Actors: Customer (initiator), Teller • Overview: the customer applies for and is granted a new bank account with some initial approved line of credit. The teller logs on to the system, selects open account , and supplies the new account details. The system prints a copy of the contents of the new account with the date, which the teller hands to the customer. Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM17

  19. Design of Bank – Identify Classes • TELLER • CUSTOMER • SAVINGS_ACCOUNT • CHEQUING_ACCOUNT • MAIN_MENU • BALANCE_INQUIRY • INTEREST_RATE ……… • Where do we start? Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM18

  20. Test Driven Development • Write a little Test • Test will not work initially (there is no code) • Might not even compile • Make the Test work quickly • Commit whatever sins are necessary in the process (e.g. duplication in the code) • Refactor • Eliminate the duplication created in merely getting the test to work Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM19

  21. EiffelStudio – create a new project Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM20

  22. Call the new project bank Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM21

  23. Compile and Run print(“hello world!”) Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM22

  24. Compile often! • Always start with a compiled system • New project wizard • Copy an existing system • A compiled system is needed for browsing • Compile often! Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM23

  25. ETester – Create a tests cluster Click here Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM24

  26. Create class ACCOUNT_TEST Click here Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM25

  27. Clusters and Classes Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM26

  28. Ace file – Directory Structure Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM27

  29. Ace File – Ace.ace http://www.cs.yorku.ca/eiffel/precompiled system "bank“ root root_class: make default precompiled ("C:\Eiffel53\precomp\spec\windows\base") assertion (check) assertion (require) … cluster root_cluster: "." alltests: ".\tests" librarybase: "$ISE_EIFFEL\library\base" exclude "table_eiffel3"; "desc"; end … end Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM28

  30. Project Configuration (Ace file) Click here Root Class All contracts ACCOUNT_TESTturned on Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM29

  31. Write Test test_create_account: BOOLEAN is local c: CUSTOMER do comment("test_create_account") create c.make("Archie Fox") Result := equal(c.name, "Archie Fox") end Error code: VTCT Error: type is based on unknown class. What to do: use an identifier that is the name of a class in the universe. Class: ACCOUNT_TEST Unknown class name: CUSTOMER Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM30

  32. The Test specifies a Design Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM31

  33. customer.e indexing description: "A bank customer“ class CUSTOMER create set_name feature -- Element change make (a_name: STRING) is -- Create a customer. Set `name' to `a_name'. require a_name_not_void: a_name /= Void do name := a_name ensure name_assigned: name = a_name end feature -- Access name: STRING -- of customer invariant name_not_void: name /= Void end Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM32

  34. ETester GUI – Green bar Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM33

  35. Test: A customer with a savings account test_create_customer_with_account: BOOLEAN is local a1,a2: SAVINGS_ACCOUNT c: CUSTOMER initial_deposit: REAL do initial_deposit := 500 create a1.make(initial_deposit) check a1.balance = initial_deposit end create c.make(a1, "Archie Fox") a2 := c.account Result := equal(c.name, "Archie Fox") and a2 = a1 and a2.balance = initial_deposit end Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM34

  36. Red bar Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM35

  37. Use debugger to find problem Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM36

  38. EiffelStudio – BON tool Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM37

  39. Client-Supplier relationship Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM38

  40. Open Account Use case (revisited) • Actors: Customer (initiator), Teller • Overview: the customer applies for and is granted a new bank account with some initial approved line of credit. The teller logs on to the system, selects open account , and supplies the new account details. The system prints a copy of the contents of the new account with the date, which the teller hands to the customer. • We have not yet dealt with the LOC, system menu and the receipt. We leave this as an exercise. Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM39

  41. Withdraw Use Case • Actors: Customer (initiator) and Teller • Overview: The customer provides the teller with an account number and a withdrawal amount. The teller selects `withdraw-request’ from the system menu, and enters the data. The System debits the account by the requested withdrawal amount, and prints a receipt with the date and the amount, which the teller gives to the customer. • Question: What happens if there is not enough money in the account to withdraw? Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM40

  42. test_withdraw test_withdraw: BOOLEAN is local sa1, sa2: SAVINGS_ACCOUNT initial_deposit: REAL do comment("test_withdraw") initial_deposit := 500 create sa1.make(initial_deposit) create sa2.make(200) sa1.withdraw(300) Result := equal(sa1, sa2) end Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM41

  43. Bank design (BON static diagram) Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM42

  44. EiffelStudio feature tool – withdraw Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM43

  45. Run tests Slides based on Object Oriented Software Construction 2020-01-03 5:35 PM44

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