1. Copyright 2002 Prentice-Hall, Inc. Chapter 2 Object-Oriented Analysis and Design Modern Systems Analysis and Design Third Edition Jeffrey A. Hoffer Joey F. George Joseph S. Valacich Chapter 5 System Modeling Sommerville, "software engineering ", 9 th Ed., 2011 20.1

2. Learning Objectives Key terms Use Case Object Object class State Behavior Operation Encapsulation Constructor Operation Query Operation Update Operation Association Multiplicity Abstract Class Concrete Class Class-Scope attribute Abstract operation Method Polymorphism Overriding Aggregation Composition Event State transition Sequence diagram 20.2

3. Learning Objectives Discuss the concepts and principles underlying the object-oriented approach Describe the activities in the different phases of the object-oriented development life cycle State the advantages of object-oriented modeling versus traditional systems development approaches Learn to develop requirements models using use- case diagrams Learn to use class diagrams to develop object models of the problem domain Learn to develop dynamic models using state, interaction and activity diagrams Model real-world applications using UML diagrams 20.3

4. Introduction Object-Oriented systems 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 20.4

5. The Object-Oriented Systems Development Life Cycle Analysis Phase Model of the real-world application is developed showing its important properties Model specifies the functional behavior of the system independent of implementation details Design Phase Analysis model is refined and adapted to the environment Can be separated into two stages  System design Concerned with overall system architecture  Object design Implementation details are added to system design 20.5

6. The Object-Oriented Systems Development Life Cycle Implementation Phase Design is implemented using a programming language or database management system 20.6

7. The Object-Oriented Systems Development Life Cycle Deliverables and Outcomes 1.The ability to tackle more challenging problem domains 2.Improved communication among users, analysts, designers and programmers 3.Increased consistency among analysis, design and programming activities 4.Explicit representation of commonality among system components 5.Reusability of analysis, design and programming results 6.Increased consistency among the models developed during object-oriented analysis, design, and programming 20.7

8. System Modeling  System modeling is the process of developing abstract models of a system, with each model presenting a different view or perspective of that system.  System modeling has now come to mean representing a system using some kind of graphical notation, which is now almost always based on notations in the Unified Modeling Language (UML).  System modelling helps the analyst to understand the functionality of the system and models are used to communicate with customers. 8

9. Existing and planned system models  Models of the existing system are used during requirements engineering. They help clarify what the existing system does and can be used as a basis for discussing its strengths and weaknesses. These then lead to requirements for the new system.  Models of the new system are used during requirements engineering to help explain the proposed requirements to other system stakeholders. Engineers use these models to discuss design proposals and to document the system for implementation.  In a model-driven engineering process, it is possible to generate a complete or partial system implementation from the system model. 9

10. 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 Activity diagrams Use cases Sequence diagrams Class diagrams State diagrams 20.10

11. UML diagram types  Activity diagrams, which show the activities involved in a process or in data processing.  Use case diagrams, which show the interactions between a system and its environment.  Sequence diagrams, which show interactions between actors and the system and between system components.  Class diagrams, which show the object classes in the system and the associations between these classes.  State diagrams, which show how the system reacts to internal and external events. 11

12. 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 20.12

13. Use-Case Modeling Applied to analyze functional requirements of the system Performed during the analysis phase to help developers understand functional requirements of the system without regard for implementation details Use Case A complete sequence of related actions initiated by an actor Actor An external entity that interacts with the system 20.13

14. Figure 20-2 Use-case diagram for a university registration system 20.14

15. Use-Case Modeling Developing Use-Case Diagrams Use cases are always initiated by an actor Use cases represent complete functionality of the system Relationships Between Use Cases Use cases may participate in relationships with other use-cases Two types  Extends Adds new behaviors or actions to a use case  Include One use case references another use case 20.15

16. Sequence diagrams  Sequence diagrams are part of the UML and are used to model the interactions between the actors and the objects within a system.  A sequence diagram shows the sequence of interactions that take place during a particular use case or use case instance.  The objects and actors involved are listed along the top of the diagram, with a dotted line drawn vertically from these.  Interactions between objects are indicated by annotated arrows. 16

17. Figure 20-24 Sequence diagram for a class registration scenario with prerequisites 20.17

18. What are Sequence Diagrams?  Sequence Diagrams are interaction diagrams that detail how operations are carried out.  Dynamic interactions between collaborating objects in the system  Represent a scenario in the system  Show a set of collaborating objects, messages passing between them, and timing.  The diagram captures the behavior of a single use case.  It shows objects and the messages that are passed between these objects for the particular use case.

19. What do Sequence Diagrams model?  capture the interaction between objects in the context of a collaboration  show object instances that play the roles defined in a collaboration  show the order of the interaction visually by using the vertical axis of the diagram to represent time what messages are sent and when show elements as they interact over time, showing interactions or interaction instances.  do not show the structural relationships between objects

20.  The purpose of Interaction diagrams is to:  Model interactions between objects  Assist in understanding how a system (a use case) actually works  Verify that a use case description can be supported by the existing classes  Identify responsibilities/operations and assign them to classes

21. Participants in a Sequence Diagram The sequence diagram consists of  Active Objects  Messages represented as solid-line arrows (Means by which objects communicate with each other )  Time represented as a vertical progression  Activation The time period during which an object performs an operation

22. Analysis Concepts: Dynamic models Entity Objects Represent the persistent information tracked by the system (Application domain objects, “Business objects”) Boundary Objects Represent the interaction between the user and the system Control Objects: Represent the control tasks performed by the system  >  Year  >  Month  >  Day  >  ChangeDateControl  >  LCDDisplayBoundary  >  ButtonBoundary

23. Dynamic Modeling Sequence Diagrams Synchronous Message A type of message in which the caller has to wait for the receiving object to finish executing the called operation before it can resume execution itself Simple Message A message that transfers control from the sender to the recipient without describing the details of the communication 20.23

24. Sequence Diagram - Objects  A life line illustrates what is happening to an object in a chronological fashion  :Name  Life line  Activation  Object

25. 25 Sequence Diagram – Time & Messages  Messages are used to illustrate communication between different active objects of a sequence diagram.  :Name1  :Name2  Message Two  Actor  Message One

26. A Simple Sequence Diagram

27. Basic Notation

28. Example : Online Shopping  In order to develop our sequence diagram we will need the use case text and the specification class diagram: Use Case Text: Buy a Product Online 1. Customer browses through catalog and selects items to buy. 2. Customer goes to checkout. 3. Customer fills out shipping information. 4. System presents full pricing information, including shipping information. 5. Customer fills in credit card information. 6. System authorizes purchase. 7. System confirms sale immediately. 8. System sends confirming email to customer.

29. Solution

30. Questions??? Thanks for your Attention! Slide 30