1. Systems Analysis and Design in a Changing World, 3rd Edition
Chapter 11: The Object-Oriented Approach to Design: Use Case Realization
Systems Analysis and Design in a Changing World, 3rd Edition

2. Learning Objectives
Explain the purpose and objectives of object- oriented design
Develop design class diagrams
Develop interaction diagrams based on the principles of object responsibility and use case controllers
Systems Analysis and Design in a Changing World, 3rd Edition

3. Learning Objectives (continued)
Develop detailed sequence diagrams as the core process in systems design
Develop collaboration diagrams as part of systems design
Document the architectural design using package diagrams
Systems Analysis and Design in a Changing World, 3rd Edition

4. Overview
Primary focus of this chapter and the next is how to develop detailed object-oriented design models
Programmers use models to code the system
Two most important models are design class diagrams and interaction diagrams (sequence diagrams and collaboration diagrams)
Class diagrams are developed for domain, view, and data access layers
Interaction diagrams extend system sequence diagrams
Systems Analysis and Design in a Changing World, 3rd Edition

5. Object-Oriented Design – The Bridge Between Analysis and Programming
Bridge between user’s requirements and new system’s programming
Object-oriented design is process by which detailed object-oriented models are built
Programmers use design to write code and test new system
User-interface, network, controls, security, and database requires design tasks and models
Systems Analysis and Design in a Changing World, 3rd Edition

6. Overview of Object-Oriented Programs
Set of objects that cooperate to accomplish result
Object contains program logic and necessary attributes in a single unit
Objects send each other messages and collaborate to support functions of main program
OO system designer provides detail for programmers
Design class diagrams, interaction diagrams, (some) statechart diagrams
Systems Analysis and Design in a Changing World, 3rd Edition

7. Object-Oriented Event-Driven
Program Flow
Systems Analysis and Design in a Changing World, 3rd Edition

8. Simplified Design Class for Student Class
Systems Analysis and Design in a Changing World, 3rd Edition

9. Object-Oriented Design Processes and Models
Diagrams developed during analysis
Use case diagrams, use case descriptions and activity diagrams, domain model class diagrams, and system sequence diagrams
Diagrams developed during design
Design class diagrams – set of object-oriented classes needed for programming, navigation between classes, attribute names and properties and method names and properties
Interaction diagrams, package diagrams
Systems Analysis and Design in a Changing World, 3rd Edition

10. Design Models with Their Respective Input Models
Systems Analysis and Design in a Changing World, 3rd Edition

11. Iterative Process of OO Design
Create preliminary design class diagrams model
Develop interaction diagrams for each use case or scenario (realization of use cases)
Return to design class diagram
Develop method names based design of interaction diagrams
Update navigation visibility and attributes
Partition design class diagram into related functions using package diagrams (subsystems or layers)
Systems Analysis and Design in a Changing World, 3rd Edition

12. Design Classes and Design Class Diagrams
Design class diagrams and detailed interaction diagrams
Use each other as inputs and developed in parallel
Design class diagram first-cut is from domain model and engineering design principles
Preliminary design class diagram used to develop interaction diagrams
Design decisions are made during development of interaction diagrams
Design class diagram is refined
Systems Analysis and Design in a Changing World, 3rd Edition

13. Design Classes and Design Class Diagrams (continued)
Design class diagram extends domain model class diagram developed during OO analysis
Shows set of problem domain classes and their association relationships
Describes design components within the classes
When developers build design class diagrams, more classes are added
Systems Analysis and Design in a Changing World, 3rd Edition

14. Design Class Symbols
UML does not distinguish between design class notation and domain model notation
Domain modeling shows users’ work environment
Design class design specifically defines software classes
UML uses stereotype notation to categorize a model element by its characteristics
Systems Analysis and Design in a Changing World, 3rd Edition

15. Standard Stereotypes Found in Design Models
Systems Analysis and Design in a Changing World, 3rd Edition

16. Standard Design Classes
Entity – design identifier for problem domain class
Persistent class – exists after system is shut down
Boundary – designed to live on system’s automation boundary
User interface and windows classes
Control – mediates between boundary and entity classes, between the view layer and domain layer
Data access – retrieve from and send data to database
Systems Analysis and Design in a Changing World, 3rd Edition

17. Design Class Notation Name – class name and stereotype information
Attributes – visibility (private or public), attribute name, type-expression, initial-value, property
Method signature – information needed to invoke (or call) the method
Method visibility, method name, type-expression (return parameter), method parameter list (incoming arguments)
Overloaded method – method with same name but two or more different parameter lists
Systems Analysis and Design in a Changing World, 3rd Edition

18. Internal Symbols Used to Define a Design Class
Systems Analysis and Design in a Changing World, 3rd Edition

19. Student Class Examples for the Domain Diagram and the Design Class Diagram
Systems Analysis and Design in a Changing World, 3rd Edition

20. Some Fundamental Design Principles
Encapsulation – each object is self-contained unit that includes data and methods that access data
Object reuse – designers often reuse same classes for windows components
Information hiding – data associated with object is not visible to outside world
Navigation visibility – object is able to view and interact with another object
Systems Analysis and Design in a Changing World, 3rd Edition

21. Navigation Visibility Between Customer and Order
Systems Analysis and Design in a Changing World, 3rd Edition

22. Coupling and Cohesion
Coupling – qualitative measure of how closely classes in a design class diagram are linked
Number of navigation arrows on design class diagram
Low: system is easier to understand and maintain
Cohesion – qualitative measure of consistency of functions within a single class
Separation of responsibility – divide low cohesive class into several highly cohesive classes
Systems Analysis and Design in a Changing World, 3rd Edition

23. Developing the First-Cut Design Class Diagram
Extend domain model class diagram:
Elaborate attributes with type and initial value information
Add navigation visibility arrows
Detailed design proceeds, use case by use case:
Interaction diagrams implement navigation
Navigation arrows are updated to be consistent
Method signatures are added to each class
Systems Analysis and Design in a Changing World, 3rd Edition

24. RMO Domain Model Class Diagram
Systems Analysis and Design in a Changing World, 3rd Edition

25. First-cut RMO Design Class Diagram
Systems Analysis and Design in a Changing World, 3rd Edition

26. Interaction Diagrams – Realizing Use Case and Defining Methods
Realization of use case done through interaction diagram development
Determine what objects collaborate by sending messages to each other to carry out use case
Sequence diagrams and collaboration diagrams represent results of design decision
Use well-established design principles such as coupling, cohesion, separation of responsibilities
Systems Analysis and Design in a Changing World, 3rd Edition

27. Partial Design Class Diagram for the Look Up Item Availability Use Case
Systems Analysis and Design in a Changing World, 3rd Edition

28. Object Responsibility
Objects responsible for system processing
Knowing about object’s own data and other classes with which it collaborates to carry out use cases
Doing activities to assist in execution of use case
Receive and process messages
Instantiate, or create, new objects required to complete use case
CRC cards – class-responsibility-collaboration
Systems Analysis and Design in a Changing World, 3rd Edition

29. Use Case Controller
System sequence diagram (SSD) shows input messages from external actors within use case
Only indicates that messages go to system
Use case controller classes are designed as collection point for incoming messages
Artifact – class invented to handle needed system function
Use case controller acts as intermediary between outside world and internal system
Systems Analysis and Design in a Changing World, 3rd Edition

30. Designing with Sequence Diagrams
Sequence diagrams used to explain object interactions and document design decisions
Documents inputs to and outputs from system for single use case or scenario
Captures interactions between system and external world as represented by actors
Inputs are messages from actor to system
Outputs are return messages showing data
Systems Analysis and Design in a Changing World, 3rd Edition

31. SSD for the Look Up Item Availability Use Case
Systems Analysis and Design in a Changing World, 3rd Edition

32. First-Cut Sequence Diagram
Start with elements from SSD
Replace :System object with use case controller
Add other objects to be included in use case
Select input message from the use case
Add all objects that must collaborate
Determine other messages to be sent
Which object is source and destination of each message?
Systems Analysis and Design in a Changing World, 3rd Edition

33. Objects included in Look Up Item Availability
Systems Analysis and Design in a Changing World, 3rd Edition

34. First-Cut Sequence Diagram for the Look Up Item Availability Use Case
Systems Analysis and Design in a Changing World, 3rd Edition

35. Guidelines for Preliminary Sequence Diagram Development
Take each input message and determine internal messages that result from that input
For that message, determine its objective
Needed information, class destination, class source, and objects created as a result
Identify complete set of classes affected by each input message
Select objects from domain class diagram
Flesh out components for each message
Systems Analysis and Design in a Changing World, 3rd Edition

36. Developing a Multilayer Design for Look up item availability
First-cut sequence diagram – classes in domain layer
Add design for user-interface classes – view layer
Forms added as windows classes to sequence diagram
Add design for data access classes – data access layer with separate classes for database
Tools build GUI and problem domain classes
Java and Visual Studio.NET
Systems Analysis and Design in a Changing World, 3rd Edition

37. Look Up Item Availability Use Case with View Layer and User-Interface Object
Systems Analysis and Design in a Changing World, 3rd Edition

38. Partial Three-Layer Design for Look Up Item Availability
Systems Analysis and Design in a Changing World, 3rd Edition

39. Developing a First-Cut Sequence Diagram for RMO Telephone Order
Design for each input message in the SSD
Design components for all messages are combined to provide comprehensive sequence diagram for entire use case
Information from SSD and first-cut design class diagram used to develop sequence diagram
Which object is source and which object is destination?
Navigation visibility – destination object must be visible to source object
Systems Analysis and Design in a Changing World, 3rd Edition

40. Completed Three-Layer Design for Look Up Item Availability
Systems Analysis and Design in a Changing World, 3rd Edition

41. SSD for the Telephone Order Scenario of the Create New Order Use Case
Systems Analysis and Design in a Changing World, 3rd Edition

42. Partial Sequence Diagram for the Telephone Order Scenario
Systems Analysis and Design in a Changing World, 3rd Edition

43. Another Partial Sequence Diagram for the Telephone Order Scenario
Systems Analysis and Design in a Changing World, 3rd Edition

44. Sequence Diagram for Telephone Order Scenario of Create New Order Use Case
Systems Analysis and Design in a Changing World, 3rd Edition

45. Developing a Multilayer Design for the Telephone Order Scenario
To reduce complexity of diagrams, extend use case scenario one message at a time
Add user interface view layer to scenario
Add single data access class
Add each message to extend design
Sequence diagrams can become complicated
Completed design provides foundation for programming the use case
Systems Analysis and Design in a Changing World, 3rd Edition

46. Telephone Order Sequence Diagram for the startOrder Message
Systems Analysis and Design in a Changing World, 3rd Edition

47. Telephone Order Sequence Diagram for the addItem Message
Systems Analysis and Design in a Changing World, 3rd Edition

48. Telephone Order Sequence Diagram for the final messages
Systems Analysis and Design in a Changing World, 3rd Edition

49. Designing with Collaboration Diagrams
Collaboration diagrams and sequence diagrams
Both are interaction diagrams
Both capture same information
Process of designing is same for both
Model used is designer’s personal preference
Sequence diagram – because use case descriptions and dialog follow sequence of steps
Collaboration diagram – emphasizes coupling
Systems Analysis and Design in a Changing World, 3rd Edition

50. The Symbols of a Collaboration Diagram
Systems Analysis and Design in a Changing World, 3rd Edition

51. A Collaboration Diagram for Look Up Item Availability
Systems Analysis and Design in a Changing World, 3rd Edition

52. A Collaboration Diagram for Create New Order
Systems Analysis and Design in a Changing World, 3rd Edition

53. Look Up Item Availability Use Case Using Iconic Symbols
Systems Analysis and Design in a Changing World, 3rd Edition

54. Updating the Design Class Diagram
Design class diagrams developed for each layer
New classes for view layer and data access layer
New classes for domain layer use case controllers
Sequence diagram’s messages used to add methods
Constructor methods,
Data get and set method
Use case specific methods
Systems Analysis and Design in a Changing World, 3rd Edition

55. Design Class, with Method Signatures, for the Order class
Systems Analysis and Design in a Changing World, 3rd Edition

56. Updated Design Class Diagram for the Domain Layer
Systems Analysis and Design in a Changing World, 3rd Edition

57. Package Diagrams – Structuring the Major Components
High-level diagram in UML to associate classes of related groups
Identifies major components of a system and dependencies
Determines final program partitions for each layer
View, domain, data access
Can divide system into subsystem and show nesting within packages
Systems Analysis and Design in a Changing World, 3rd Edition

58. Partial Design of a Three-Layer Package Diagram for RMO
Systems Analysis and Design in a Changing World, 3rd Edition

59. RMO Subsystem Packages
Systems Analysis and Design in a Changing World, 3rd Edition

60. Implementation Issues for Three-Layer Design
Construct system with programming
Java or VB.NET
IDE tools (JBuilder, Visual Studio) provides help
Integration with user-interface design, database design, and network design
Use object responsibility to define program responsibilities for each layer
(View, domain, data access)
Systems Analysis and Design in a Changing World, 3rd Edition

61. Summary
Object-oriented design is the bridge between user requirements (in analysis models) and final system (constructed in programming language)
Systems design is driven by use cases, design class diagrams, and sequence diagrams
Domain class diagrams are transformed into design class diagrams
Sequence diagrams are extensions of system sequence diagrams
Systems Analysis and Design in a Changing World, 3rd Edition

62. Summary (continued) Object-oriented design principles must be applied
Encapsulation – data fields are placed in classes along with methods to process that data
Coupling – connectivity between classes
Cohesion – nature of an individual class
Navigation – access classes have to other classes
Object responsibilities – which messages are sent and received
Three-layer design is used because maintainable
Systems Analysis and Design in a Changing World, 3rd Edition