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CHAPTER 6 — Unit C

An Introduction to Object-Oriented Systems Analysis and Design with UML and the Unified Process McGraw-Hill, 2004 Stephen R. Schach srs@vuse.vanderbilt.edu. CHAPTER 6 — Unit C. THE ANALYSIS WORKFLOW I. Continued from Unit 6B. Buy a Masterpiece Use Case (contd). Item 1:

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CHAPTER 6 — Unit C

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  1. An Introduction toObject-Oriented Systems Analysis and Design with UML and the Unified ProcessMcGraw-Hill, 2004Stephen R. Schachsrs@vuse.vanderbilt.edu

  2. CHAPTER 6 — Unit C THE ANALYSIS WORKFLOW I

  3. Continued from Unit 6B

  4. Buy a Masterpiece Use Case (contd) • Item 1: • In paragraph 1 of this scenario, Osbert inputs the details of the masterpiece he is considering buying • In the collaboration diagram, this is modeled by message • 1: Give masterpiece details • from Osbert to the object : User Interface Class

  5. Buy a Masterpiece Use Case (contd) • Item 2: • In paragraphs 2 and 3 of the scenario, the maximum purchase price is computed by comparing the masterpiece under consideration with masterpieces that have previously been auctioned • This computation is performed by an instance of the control class, namely, object : Compute Masterpiece Price Class • To do this, details of the masterpiece under consideration need to be transferred from object : User Interface Class to object : Compute Masterpiece Price Class • This is modeled by message • 2: Transfer masterpiece details

  6. Buy a Masterpiece Use Case (contd) • Item 3: • To do the comparison, object : Compute Masterpiece Price Class has to create a masterpiece object • It first creates an instance of Masterpiece Class • This is modeled by message • 3: Create new object from : Compute Masterpiece Price Class to : Masterpiece Class • The [new] inside the object indicates that it is created as a consequence of the message • The new object is passed back to : Compute Masterpiece Price Class, modeled by message • 4: Return new object

  7. Buy a Masterpiece Use Case (contd) • Item 4: • : Compute Masterpiece Price Class compares the masterpiece under consideration with each of the previously auctioned masterpieces • It browses through all the instances of Auctioned Painting Class • This is modeled by message • 5: Browse auctioned paintings from : Compute Masterpiece Price Class to : Auctioned Painting Class and by message • 6: Return auctioned painting in the reverse direction

  8. Buy a Masterpiece Use Case (contd) • Item 5: • Having found the best match, : Compute Masterpiece Price Class computes the maximum price to be offered and informs Osbert what that price is • The price is transferred from : Compute Masterpiece Price Class to the user interface object : User Interface Class so that the price can be displayed • This is modeled by message • 7: Provide price • Next the price is displayed for Osbert by the message • 8: Display price

  9. Buy a Masterpiece Use Case (contd) • Item 6: • Osbert makes an offer for the masterpiece • The comment below paragraph 3 of the scenario states that the offer is accepted • Osbert now enters details provided by the seller • This is modeled by message • 9: Give seller details from Osbert to object : User Interface Class • The note indicates that the data are provided by the seller to Osbert

  10. Buy a Masterpiece Use Case (contd) • Item 7: • The seller data are passed on to object : Compute Masterpiece Price Class • This is modeled by message • 10: Transfer seller details to update the details of the masterpiece object : Masterpiece Class • This is modeled by message • 11: Request update

  11. Buy a Masterpiece Use Case (contd) • Item 8: • : Masterpiece Class then sends an acknowledgment to : Compute Masterpiece Price Class • This is modeled by message • 12: Send acknowledgment • This acknowledgment is then passed on to the user interface object : User Interface Class • This is modeled by message • 13: Send acknowledgment • : User Interface Class now displays it for Osbert • This is modeled by message • 14: Display acknowledgment

  12. Buy a Masterpiece Use Case (contd) • Osbert will not approve the specification document unless he understands it • Accordingly, a written description of the collaboration diagram is needed • The flow of events

  13. Buy a Masterpiece Use Case (contd) • The flow of events of the collaboration diagram of the realization of the scenario of the use case

  14. Buy a Masterpiece Use Case (contd) • UML supports two different types of interaction diagram • Collaboration diagram • Sequence diagram • Both contain exactly the same information, but displayed in different ways

  15. Buy a Masterpiece Use Case (contd) • Sequence diagram equivalent to the collaboration diagram (of the realization of the scenario of the use case)

  16. Buy a Masterpiece Use Case (contd) • The vertical lines are called lifelines • The narrow rectangle on a lifeline shows when the relevant object is active • In the collaboration diagram, the [new] is inside the : Masterpiece Class object • In the sequence diagram, the object is shifted down so that its lifeline starts where the object is created

  17. Buy a Masterpiece Use Case (contd) • The sequence diagram shows that every message of the scenario involves either • The instance of the user interface class : User Interface Class or • The instance of the control class : Compute Masterpiece Price Class

  18. Buy a Masterpiece Use Case (contd) • It also shows that every transfer of information from object A to object B is eventually followed by a transfer in the reverse direction • These two facts are also true in the fully equivalent collaboration diagram but are not as obvious in that format

  19. Interaction Diagrams • Information system developers can choose whether to use • A sequence diagram, or • A collaboration diagram, or • Both for each scenario

  20. Interaction Diagrams • The strength of a sequence diagram is that it shows the flow of messages and their order unambiguously • When transfer of information is the focus of attention, a sequence diagram is superior to a collaboration diagram • A collaboration diagram is similar to a class diagram • When the systems analysts are concentrating on the classes, a collaboration diagram is more useful than the equivalent sequence diagram

  21. Buy a Masterpiece Use Case (contd) • The seven previous figures depict different aspects of the use case Buy a Masterpiece • They use different notations and provide different levels of detail of the same activity • Why do we construct so many related artifacts? • We examine this one activity from a variety of different perspectives to learn enough about it to ensure that the analysis workflow will be correct

  22. Buy a Masterwork Use Case (contd) • The maximum price of a masterwork is computed by first treating the painting as if it were a masterpiece, and then adjusting the result

  23. Buy a Masterwork Use Case (contd) • The classes that enter into this use case are then: • User Interface Class • This class models the user interface • Compute Masterwork Price Class • This class models the computation of the price Osbert should offer • It creates a masterwork object and passes it to Compute Masterpiece Price Class as if it were a masterpiece • Compute Masterpiece Price Class • Masterpiece Class • The computation involves comparing the “masterpiece” being considered with the masterpieces that have been previously auctioned • Auctioned Painting Class • These masterpieces are instances of Auctioned Painting Class

  24. Buy a Masterwork Use Case (contd) • Class diagram showing the classes that realize the Buy a Masterwork use case

  25. Buy a Masterwork Use Case (contd) • One possible scenario of the use case

  26. Buy a Masterwork Use Case (contd) • The collaboration diagram of the scenario of the use case

  27. Buy a Masterwork Use Case (contd) • The main difference between this collaboration diagram and the one for Buy a Masterpiece is: • Object : Compute Masterwork Price Class creates a masterwork object (3: Create new object) and passes it to : Compute Masterpiece Price Class (5: Transfer masterwork) to compute the maximum asking price as if the painting were a masterpiece • This price is passed back to : Compute Masterwork Price Class (8: Provide price), which adjusts the price to reflect the fact that the painting in question is indeed a masterwork and not a masterpiece (9: Adjust price)  

  28. Buy a Masterwork Use Case (contd) • The flow of events of the collaboration diagram of the realization of the scenario of the use case

  29. Buy a Masterwork Use Case (contd) • Sequence diagram equivalent to the collaboration diagram (of the realization of the scenario of the use case)

  30. Buy Other Painting Use Case • Class diagram

  31. Buy Other Painting Use Case (contd) • Scenarios and interaction diagrams (collaboration diagram, sequence diagram), and associated flows of events are left as an exercise (Problems 6.11 through 6.14)

  32. Modifying the Main Menu • The main menu has to be modified to reflect buying the three different types of painting explicitly • Buy a painting must replaced by Buy a masterpiece, Buy a masterwork, and Buy other painting • The revised screen is generated by : User Interface Class

  33. Modifying the Main Menu (contd) • The corresponding textual interface is:

  34. Sell a Painting Use Case (contd) • Class diagram • The realization is straightforward

  35. Continued in Unit 6D

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