Appendix 3 Object-Oriented Analysis and Design

1. Modern Systems Analysisand DesignFourth EditionJeffrey A. Hoffer Joey F. GeorgeJoseph S. Valacich Appendix 3 Object-Oriented Analysis and Design

2. Learning Objectives • Define events, state transitions, and sequence diagrams. • Describe concepts and principles of object-orientation. • Describe activities of the different phases of object-oriented development. • Compare object-oriented modeling with traditional systems development approaches. • Develop dynamic models with state, interaction, and activity diagrams. • Model real-world applications with UML.

3. The Object-Oriented Development Life Cycle • Process of progressively developing representation of a system component (or object) through the phases of analysis, design, and implementation • The model is abstract in the early stages • As the model evolves, it becomes more and more detailed

4. Object oriented cycle is like an onion, evolving from abstract to detailed, from external qualities to system architecture and algorithms.

5. Object-Oriented Deliverables and Outcomes • The ability to tackle more challenging problem domains • Improved communication among users, analysts, designers, and programmers • Increased consistency among analysis, design, and programming activities • Explicit representation of commonality among system components • Robust systems • Reusability of analysis, design, and programming results • Increased consistency among the models developed during object-oriented analysis, design, and programming

6. The Unified Modeling Language (UML) • A notation that allows the modeler to specify, visualize, and construct the artifacts of software systems, as well as business models • Techniques and notations: • Use cases • Class diagrams • State diagrams • Sequence diagrams • Activity diagrams

7. Use Cases Revisited • A depiction of a system’s behavior or functionality under various conditions as the system responds to requests from users • Full functioning for a specific business purpose • See Chapter 7

9. Class Diagrams Revisited • Features: • Objects and classes • Encapsulation of attributes and operations • Polymorphism • Inheritance • Aggregation and composition • See Chapter 9

11. Dynamic Modeling • Representation of activities that occur throughout the lifetime of a system • Types of UML dynamic models • State diagram: state changes within an object • Sequence diagram: time-sequenced interactions between objects • Activity diagram: flow of control between activities within an object

12. State Diagrams • State • A condition during the life of an object during which it satisfies some conditions, performs some actions or waits for some events • Shown as a rectangle with rounded corners • State Transition • The changes in the attribute of an object or in the links an object has with other objects • Shown as a solid arrow • Diagrammed with a guard condition and action • Event • Something that takes place at a certain point in time, triggering a state transition

13. Guard condition Action Guard condition A transition is labeled with a guard condition and/or an action, separated with a forward slash / State diagram: a model of the states of a single object and the events that cause the object to change from one state to another

14. Diagramming Substates and Decomposing States A state can be expanded into substates using nested state diagrams, similar to expansion of processes in different levels of DFDs.

15. Diagramming Substates and Decomposing States An event can be expanded into using nested state diagrams, and may involve substates and subtransitions and events.

16. Dynamic Modeling:Sequence Diagrams • A depiction of the interaction among objects during certain periods of time • Elements of a sequence diagram • Objects: represented by boxes at top of diagram • Lifeline: the time during which an object exists • Activation: the time period during which an object performs an operation • Messages: means by which objects communicate with each other

17. Types of Messages in Sequence Diagrams • Synchronous message • The caller must wait for the receiving object to finish executing the called operation before it can resume execution itself • Asynchronous message • The caller can resume execution right after sending the message, without waiting for the receiver to complete • Simple message • A message that transfers control from the sender to the recipient without describing the details of the communication 20.17

18. object time lifeline message activation

19. Process Modeling:Activity Diagrams • Shows the conditional logic for the sequence of system activities needed to accomplish a business process • Clearly shows parallel and alternative behaviors • Can be used to show the logic of a use case

20. Elements of Activity Diagrams • Activity: a behavior that an object carries out while in a particular state • Transition: a movement from one activity or state to another • Branch: a diamond symbol containing a condition whose results provide transitions to different paths of activities • Synchronization bar: horizontal or vertical bars denoting parallel or concurrent paths of activities • Fork: the beginning of parallel activities • Join: the end of parallel activities • Swimlanes: columns representing different organizatonal units of the system

21. branch activity synchronization bar swimlane

22. Analysis Versus Design • Start with existing set of analysis model • Progressively add technical details • Design model must be more detailed than analysis model • Component Diagram • A diagram that shows the software components or modules and their dependencies • Deployment Diagram • A diagram that shows how the software components, process and objects are deployed into the physical architecture of the system

24. Summary • In this chapter you learned how to: • Define events, state transitions, and sequence diagrams. • Describe concepts and principles of object-orientation. • Describe activities of the different phases of object-oriented development. • Compare object-oriented modeling with traditional systems development approaches. • Develop dynamic models with state, interaction, and activity diagrams. • Model real-world applications with UML.