Programming Logic and Design Fifth Edition, Comprehensive

1. Programming Logic and DesignFifth Edition, Comprehensive Chapter 13 System Modeling with the UML

2. Objectives • Understand the need for system modeling • Be able to describe the UML • Understand use case diagrams • Understand class and object diagrams • Understand sequence and communication diagrams Programming Logic and Design, Fifth Edition, Comprehensive

3. Objectives (continued) • Understand state machine diagrams • Understand activity diagrams • Understand component and deployment diagrams • Be able to diagram exception handling • Be able to decide when to use the UML and which UML diagrams to use Programming Logic and Design, Fifth Edition, Comprehensive

4. Understanding the Need for System Modeling • Most programs are part of a larger system • System design: specification of how all parts of the system are implemented and coordinated • Some guidelines: • Large systems are easier to understand when broken down into subsystems • The larger the system, the more important are modeling techniques • Good models promote communication in the development team Programming Logic and Design, Fifth Edition, Comprehensive

5. Understanding the Need for System Modeling (continued) • Unified Modeling Language (UML) • Popular design tool • Allows you to break a system into subsystems • Hides implementation details • Means for programmers and businesspeople to communicate about system design • Plan division of responsibilities Programming Logic and Design, Fifth Edition, Comprehensive

6. What is UML? • UML • Standard way to specify, construct, and document systems • Modeling language, not a programming language • Creates top-view diagrams of business processes • Designed to be nontechnical in nature Programming Logic and Design, Fifth Edition, Comprehensive

7. What is UML? (continued) • UML has 13 diagram types in three major categories: • Structure diagrams • Behavior diagrams • Interaction diagrams • Each type supports multiple variations Programming Logic and Design, Fifth Edition, Comprehensive

8. What is UML? (continued) • Structure diagrams: • Class diagrams • Object diagrams • Component diagrams • Composite structure diagrams • Package diagrams • Deployment diagrams Programming Logic and Design, Fifth Edition, Comprehensive

9. What is UML? (continued) • Behavior diagrams: • Use case diagrams • Activity diagrams • State machine diagrams • Interaction diagrams: • Sequence diagrams • Communication diagrams • Timing diagrams • Interaction overview diagrams Programming Logic and Design, Fifth Edition, Comprehensive

10. Using Use Case Diagrams • Use case diagram: • Shows how a business works from the perspective of someone outside the business • Includes users (employees, customers, suppliers) • Represents only the functions that are visible to the system’s actors • Analyze the main events in a system to establish use cases Programming Logic and Design, Fifth Edition, Comprehensive

11. Figure 13-1 Use case diagram for librarian Programming Logic and Design, Fifth Edition, Comprehensive

12. Using Use Case Diagrams (continued) • Each use case has at least one main scenario, but may also have more that are variations • Three variations in use cases: • Extend • Include • Generalization • Extend variation • Shows functions beyond those in the base case • Usually an optional activity Programming Logic and Design, Fifth Edition, Comprehensive

13. Figure 13-2 Use case diagram for librarian with scenario extension Programming Logic and Design, Fifth Edition, Comprehensive

14. Using Use Case Diagrams (continued) • Stereotype: adds more meaning to the UML vocabulary of shapes • Add “<<extend>>” near the relationship line • Include variation: • When a case can be part of multiple use cases • Shown with an oval and a dashed arrow • Generalization variation: • When you want to substitute a more specific case for a general one • Use open-headed dashed arrows Programming Logic and Design, Fifth Edition, Comprehensive

15. Figure 13-3 Use case diagram for librarian using stereotype Programming Logic and Design, Fifth Edition, Comprehensive

16. Figure 13-4 Use case diagram for librarian using include relationship Programming Logic and Design, Fifth Edition, Comprehensive

17. Figure 13-5 Use case diagram for librarian with generalizations Programming Logic and Design, Fifth Edition, Comprehensive

18. Using Use Case Diagrams (continued) • Use case diagrams may show multiple actors • Use case diagrams are only tools to aid communication • Keep them visually pleasing and not overcrowded • Use separate diagrams for different points of view: • Might emphasize actors and their relationships • Might emphasize actions and hide some of the specific actors to keep it simple Programming Logic and Design, Fifth Edition, Comprehensive

19. Figure 13-6 Use case diagram for librarian with multiple actors Programming Logic and Design, Fifth Edition, Comprehensive

20. Figure 13-7 Use case diagram emphasizing actors Programming Logic and Design, Fifth Edition, Comprehensive

21. Figure 13-8 Use case diagram emphasizing system requirements Programming Logic and Design, Fifth Edition, Comprehensive

22. Using Class and Object Diagrams • Class diagrams: • Illustrate names, attributes, and methods • More useful to programmers than users • Class diagram is a rectangle with three sections: • Top: name of the class • Middle: names of attributes • Bottom: names of methods Figure 13-9Book class diagram Programming Logic and Design, Fifth Edition, Comprehensive

23. Using Class and Object Diagrams (continued) • Use generalizations with class diagrams to show: • More general (parent) classes • More specific (child) classes that inherit attributes from parents • Association relationship: • Describes the connection between objects • May include information about arithmetic relationships such as cardinality or multiplicity • Shown with a straight line between classes Programming Logic and Design, Fifth Edition, Comprehensive

24. Figure 13-10LibraryItem class diagram showing generalization Programming Logic and Design, Fifth Edition, Comprehensive

25. Figure 13-11 Class diagram with association relationship Programming Logic and Design, Fifth Edition, Comprehensive

26. Figure 13-12 Class diagram with several association relationships Programming Logic and Design, Fifth Edition, Comprehensive

27. Using Class and Object Diagrams (continued) • Whole-part relationship: • One or more classes make up the parts of a larger whole class • Also called an aggregation • Use open diamond at the “whole part” end of the line • Represents a “has-a” relationship • Object diagram • Models specific instances of classes • Shows a snapshot of an object at one point in time • Can use class diagrams or object diagrams interchangeably to suit your needs Programming Logic and Design, Fifth Edition, Comprehensive

28. Figure 13-13 Class diagram with whole-part relationship Programming Logic and Design, Fifth Edition, Comprehensive

29. Figure 13-14 Object diagram for Library Programming Logic and Design, Fifth Edition, Comprehensive

30. Using Sequence and Communication Diagrams • Sequence diagram: • Shows timing of events in a single use case • Horizontal axis represents objects • Vertical axis represents time • Vertical dashed line from x-axis to object shows period of time that the object exists • Horizontal arrows show communication between objects over time Programming Logic and Design, Fifth Edition, Comprehensive

31. Figure 13-15 Sequence diagram for checking out a Book for a Patron Programming Logic and Design, Fifth Edition, Comprehensive

32. Using Sequence and Communication Diagrams (continued) • Communication diagram: • Emphasizes the organization of objects in a system • Contains sequence numbers to show the precise order in which activities occur • Focus is on object roles Programming Logic and Design, Fifth Edition, Comprehensive

33. Figure 13-16 Communication diagram for Book class Programming Logic and Design, Fifth Edition, Comprehensive

34. Using State Machine Diagrams • State machine diagram: • Shows the different statuses of a class or object at different points in time • Use rounded rectangles for each state and labeled arrows to show sequence of events that affect the state • Solid dot indicates start and stop states for a class or object Programming Logic and Design, Fifth Edition, Comprehensive

35. Figure 13-17 State machine diagram for checking out a Book for a Patron Programming Logic and Design, Fifth Edition, Comprehensive

36. Using Activity Diagrams • Activity diagram: • Resembles a flowchart • Shows flow of actions in the system • Use flowchart start and stop symbols (lozenges) to describe actions • Use solid dots to show start and stop states • Use diamonds for decisions, with possible outcomes shown along the branches Programming Logic and Design, Fifth Edition, Comprehensive

37. Figure 13-18 Activity diagram showing branch Programming Logic and Design, Fifth Edition, Comprehensive

38. Using Activity Diagrams (continued) • Forks and joins: • Used to show simultaneous activities • Indicated by thick straight lines • Fork: • Defines a branch in which all paths are followed simultaneously Programming Logic and Design, Fifth Edition, Comprehensive

39. Using Activity Diagrams (continued) • Join: • Reunites the flow of control after a fork • Time signal: • Indicates that a specific amount of time has passed before an action is started • Shaped like an hourglass Programming Logic and Design, Fifth Edition, Comprehensive

40. Figure 13-19 Activity diagram showing fork and join Programming Logic and Design, Fifth Edition, Comprehensive

41. Figure 13-20 A time signal starting an action Programming Logic and Design, Fifth Edition, Comprehensive

42. Using Component and Deployment Diagrams • Component diagram: • Used to emphasize files, databases, documents, and components used by a system’s software • Deployment diagram: • Focuses on a system’s hardware Programming Logic and Design, Fifth Edition, Comprehensive

43. Figure 13-21 Component diagram Programming Logic and Design, Fifth Edition, Comprehensive

44. Figure 13-22 Deployment diagram Programming Logic and Design, Fifth Edition, Comprehensive

45. Diagramming Exception Handling • Program code uses try-catch blocks to trap errors and handle them • Protected node: • A try block in UML • Use a rounded rectangle • Exceptions that may be thrown are shown as lightning bolts • Handler body node: a catch block in UML Programming Logic and Design, Fifth Edition, Comprehensive

46. Figure 13-23 Exceptions in the Book check-out activity Programming Logic and Design, Fifth Edition, Comprehensive

47. Deciding Which UML Diagrams to Use • UML widely recognized modeling standard • Criticisms of UML • Size: UML too large and complex • Many diagrams infrequently used • Several are redundant • Imprecision: UML a combination of rules and English • Problems when diagrams applied to tasks not implemented in OO languages • Complexity: UML relatively difficult to learn Programming Logic and Design, Fifth Edition, Comprehensive

48. Deciding Which UML Diagrams to Use (continued) • Each type of UML diagram provides a different view of a system • No view is superior to the others • Most complete picture is achieved by several views • UML diagrams are a communication tool Programming Logic and Design, Fifth Edition, Comprehensive

49. Summary • UML allows programmers and businesspeople to communicate about system design • UML has 13 diagram types • Use case diagram shows how business works from the standpoint of those who use the business • Class diagram illustrates the names, attributes, and methods of a class or set of classes Programming Logic and Design, Fifth Edition, Comprehensive

50. Summary (continued) • Object diagram models a specific instance of a class at one point in time • Sequence diagram shows the timing of events in a single use case • Communication diagram shows the organization of objects in a system • State machine diagram shows status of a class or object at a specific point in time Programming Logic and Design, Fifth Edition, Comprehensive