Systems Analysis & Design Tenth Edition PDF

Systems Analysis & Design Tenth Edition Global Edition Chapter 10 Object-Oriented Systems Analysis and Design Using UML Copyright © 2020 Pearson Education Ltd. Le...

Systems Analysis & Design Tenth Edition Global Edition Chapter 10 Object-Oriented Systems Analysis and Design Using UML Copyright © 2020 Pearson Education Ltd. Learning Objectives (1 of 2) 10.1 Understand what object-oriented systems analysis and design is and appreciate its usefulness 10.2 Comprehend the concepts of Unified Modeling Language (UML), the standard approach for modeling a system in the object-oriented world 10.3 Apply the steps used in UML to break down the system into a use case model and then a class model Copyright © 2020 Pearson Education Ltd. Learning Objectives (2 of 2) 10.4 Diagram systems with the UML toolset so they can be described and properly designed 10.5 Document and communicate the newly modeled object-oriented system to users and other analysts Copyright © 2020 Pearson Education Ltd. Object-Oriented Analysis and Design (1 of 2) Works well in situations where complicated systems are undergoing continuous maintenance, adaptation, and design Objects, classes are reusable The Unified Modeling Language (UML) is an industry standard for modeling object-oriented systems. Copyright © 2020 Pearson Education Ltd. Object-Oriented Analysis and Design (2 of 2) Reusability – Recycling of program parts should reduce the costs of development in computer-based systems Maintaining systems – Making a change in one object has a minimal impact on other objects Copyright © 2020 Pearson Education Ltd. Major Topics Object-oriented concepts CRC cards and object think Unified Modeling Language Use case and other UML diagrams Packages Using UML Copyright © 2020 Pearson Education Ltd. Object-Oriented Concepts Objects Classes Inheritance Copyright © 2020 Pearson Education Ltd. Objects Persons, places, or things that are relevant to the system being analyzed May be customers, items, orders, and so on May be GUI displays or text areas on a display Copyright © 2020 Pearson Education Ltd. Classes Defines the set of shared attributes and behaviors found in each object in the class Should have a name that differentiates it from all other classes Instantiate is when an object is created from a class An attribute describes some property that is possessed by all objects of the class A method is an action that can be requested from any object of the class Copyright © 2020 Pearson Education Ltd. Figure 10.1 An Example of a UML Class Copyright © 2020 Pearson Education Ltd. Inheritance (1 of 2) When a derived class inherits all the attributes and behaviors of the base class Reduces programming labor by using common objects easily A feature only found in object-oriented systems Copyright © 2020 Pearson Education Ltd. Figure 10.2 A Class Diagram Showing Inheritance Car and truck are specific examples of vehicles and inherit the characteristics of the more general class vehicle. Copyright © 2020 Pearson Education Ltd. CRC Cards and Object Think CRC – Class – Responsibilities – Collaborators CRC cards are used to represent the responsibilities of classes and the interaction between the classes Copyright © 2020 Pearson Education Ltd. Figure 10.3 Four CRC Cards Copyright © 2020 Pearson Education Ltd. Interacting during a CRC Session Identify all the classes you can Create scenarios Identify and refine responsibilities Copyright © 2020 Pearson Education Ltd. The Unified Modeling Language (UML) Concepts and Diagrams Things Relationships Diagrams Copyright © 2020 Pearson Education Ltd. Things Structural things are: – Classes, interfaces, use cases, and other elements that provide a way to create models – They allow the user to describe relationships Behavioral things Describe how things work – Interactions and state machines Group things – Used to define boundaries Annotational things – Can add notes to the diagrams Copyright © 2020 Pearson Education Ltd. Relationships (1 of 2) Structural relationships – Tie things together in structural diagrams Behavioral relationships – Used in behavioral diagrams Copyright © 2020 Pearson Education Ltd. Structural Relationships Dependencies Aggregations Associations Generalizations Copyright © 2020 Pearson Education Ltd. Behavioral Relationships Communicates Includes Extends Generalizes Copyright © 2020 Pearson Education Ltd. Diagrams Structural diagrams – Used to describe the relation between classes Behavioral diagrams – Used to describe the interaction between people (actors) and a use case (how the actors use the system) Copyright © 2020 Pearson Education Ltd. Structural Diagrams Class diagrams Object diagrams Component diagrams Deployment diagrams Copyright © 2020 Pearson Education Ltd. Behavioral Diagrams Use case diagrams Sequence diagrams Collaboration diagrams Statechart diagrams Activity diagrams Copyright © 2020 Pearson Education Ltd. Figure 10.4 An Overall View of UML and Its Components: Things, Relationships, and Diagrams (1 of 2) UML Category UML Elements Specific UML Details Things Structural Things Classes Interfaces Collaborations Use Cases Active Classes Components Nodes Things Behavioral Things Interactions State Machines Things Grouping Things Packages Things Annotational Notes Things Relationships Structural Dependencies Relationships Aggregations Associations Generalizations Copyright © 2020 Pearson Education Ltd. Figure 10.4 An Overall View of UML and Its Components: Things, Relationships, and Diagrams (2 of 2) UML Category UML Elements Specific UML Details Relationships Behavioral Communicates Relationships Includes Extends Generalizes Diagrams Structural Class Diagrams Diagrams Component Diagrams Deployment Diagrams Diagrams Behavioral Use Case Diagrams Diagrams Sequence Diagrams Communication Diagrams Statechart Diagrams Activity Diagrams Copyright © 2020 Pearson Education Ltd. Commonly Used UML Diagrams (1 of 2) Use case diagram – Describing how the system is used – The starting point for UML modeling Use case scenario – A verbal articulation of exceptions to the main behavior described by the primary use case Activity diagram – Illustrates the overall flow of activities Copyright © 2020 Pearson Education Ltd. Commonly Used UML Diagrams (2 of 2) Sequence diagrams – Show the sequence of activities and class relationships Class diagrams – Show classes and relationships Statechart diagrams – Show the state transitions Copyright © 2020 Pearson Education Ltd. Figure 10.5 An Overview of UML Diagrams Showing How Each Diagram Leads to the Development of Other UML Diagrams Copyright © 2020 Pearson Education Ltd. Use Case Modeling Describes what the system does, without describing how the system does it Based on the interactions and relationships of individual use cases Use case describes – Actor – Event – Use case Copyright © 2020 Pearson Education Ltd. Figure 10.6 A Use Case Example of Student Enrollment Copyright © 2020 Pearson Education Ltd. Figure 10.7 A Use Case Scenario is Divided into Three Sections: Identification and Initiation, Steps Performed, and Conditions, Assumptions, and Questions Copyright © 2020 Pearson Education Ltd. Activity Diagrams Show the sequence of activities in a process, including sequential and parallel activities, and decisions that are made Symbols – Rectangle with rounded ends – Arrow – Diamond – Long, flat rectangle – Filled-in circle – Black circle surrounded by a white circle – Swimlanes Copyright © 2020 Pearson Education Ltd. Figure 10.8 Specialized Symbols are Used to Draw an Activity Diagram Copyright © 2020 Pearson Education Ltd. Creating Activity Diagrams Created by asking what happens first, what happens second, and so on Must determine what activities are done in sequence or in parallel The sequence of activities can be determined from physical data flow diagrams Can be created by examining all the scenarios for a use case Copyright © 2020 Pearson Education Ltd. Swimlanes Useful to show how the data must be transmitted or converted Help to divide up the tasks in a team Makes the activity diagram one that people want to use to communicate with others Copyright © 2020 Pearson Education Ltd. Figure 10.9 This Activity Diagram Shows Three Swimlanes: Client Web Page, Web Server, and Mainframe Copyright © 2020 Pearson Education Ltd. Activity Diagrams and Test Plans Activity diagrams may be used to construct test plans Each event must be tested to see if the system goes to the next state Each decision must be tested Copyright © 2020 Pearson Education Ltd. Activity Diagrams Not Created for All Use Cases Use an activity diagram when: – It helps to understand the activities of a use case – The flow of control is complex – There is a need to model workflow – When all scenarios for a use case need to be shown Copyright © 2020 Pearson Education Ltd. Sequence Diagrams Illustrate a succession of interactions between classes or object instances over time Often used to show the processing described in use case scenarios Used to show the overall pattern of the activities or interactions in a use case Copyright © 2020 Pearson Education Ltd. Figure 10.10 Specialized Symbols Used to Draw a Sequence Diagram Copyright © 2020 Pearson Education Ltd. Figure 10.11 A Sequence Diagram for Student Admission: Sequence Diagrams Emphasize the Time Ordering of Messages Copyright © 2020 Pearson Education Ltd. Communication Diagrams Describes the interactions of two or more things in the system that perform a behavior that is more than any one of the things can do alone Shows the same information as a sequence diagram, but may be more difficult to read Emphasizes the organization of objects Made up of objects, communication links, and the messages that can be passed along those links Copyright © 2020 Pearson Education Ltd. Figure 10.12 A Communication Diagram for Student Admission Communication diagrams show the same information that is depicted in a sequence diagram but emphasize the organization of objects rather than the time ordering. Copyright © 2020 Pearson Education Ltd. Class Diagrams (1 of 2) Show the static features of the system and do not represent any particular processing Show the nature of the relationships between classes Show data storage requirements as well as processing requirements Copyright © 2020 Pearson Education Ltd. Class Diagrams (2 of 2) Classes Attributes – Private – Public – Protected Methods – Standard – Custom Copyright © 2020 Pearson Education Ltd. Figure 10.13 A Class Diagram for Course Offerings: the Filled-In Diamonds Show Aggregation and the Empty Diamond Shows a Whole-Part Relationship Copyright © 2020 Pearson Education Ltd. Method Overloading Including the same method (or operation) several times in a class The same method may be defined more than once in a given class, as long as the parameters sent as part of the message are different Copyright © 2020 Pearson Education Ltd. Types of Classes Entity classes Interface classes Abstract classes Control classes Copyright © 2020 Pearson Education Ltd. Entity Classes Represent real-world items The entities represented on an entity-relationship diagram Copyright © 2020 Pearson Education Ltd. Interface or Boundary Classes Provide a means for users to work with the system Human interfaces may be a display, window, Web form, dialogue box, touch-tone telephone, or other way for users to interact with the system System interfaces involve sending data to or receiving data from others Copyright © 2020 Pearson Education Ltd. Abstract Classes (1 of 2) Linked to concrete classes in a generalization/specialization relationship Cannot be directly instantiated Copyright © 2020 Pearson Education Ltd. Control Classes Used to control the flow of activities Many small control classes can be used to achieve classes that are reusable Copyright © 2020 Pearson Education Ltd. Presentation, Business, and Persistence Layers Sequence diagrams may be discussed using three layers: – Presentation layer, what the user sees, corresponding to the interface or boundary classes – Business layer, containing the unique rules for this application, corresponding roughly to control classes – Persistence or data access layer, for obtaining and storing data, corresponding to the entity classes Copyright © 2020 Pearson Education Ltd. Defining Messages and Methods Each message may be defined using a notation similar to that described for the data dictionary The methods may have logic defined using structured English, a decision table, or a decision tree Copyright © 2020 Pearson Education Ltd. Figure 10.15 A Sequence Diagram for Using Two Web Pages: One for Student Information, One for Course Information Copyright © 2020 Pearson Education Ltd. Create Sequence Diagrams Include the actor from the use case diagram Define one or more interface classes for each actor Each use case should have one control class Examine the use case to see what entity classes are required The sequence diagram may be modified when doing detailed design Copyright © 2020 Pearson Education Ltd. Creating a Test Plan from a Sequence Diagram Does each method return correct results? Ensure that entity classes store or obtain the correct attribute values Verify that all JavaScript paths work correctly Ensure that the server control classes work correctly Ask, “What may fail?” Determine what to do if something can fail Copyright © 2020 Pearson Education Ltd. Relationships (2 of 2) The connections between classes – Associations – Whole/part Copyright © 2020 Pearson Education Ltd. Figure 10.18 An Example of an Associative Class in Which a Particular Section Defines the Relationship between a Student and a Course Copyright © 2020 Pearson Education Ltd. Associations The simplest type of relationship Association classes are those that are used to break up a many-to-many association between classes An object in a class may have a relationship to other objects in the same class, called a reflexive association Copyright © 2020 Pearson Education Ltd. Whole/Part Relationships When one class represents the whole object, and other classes represent parts Categories – Aggregation – Collection – Composition Copyright © 2020 Pearson Education Ltd. Aggregation A “has a” relationship Provides a means of showing that the whole object is composed of the sum of its parts Copyright © 2020 Pearson Education Ltd. Collection Consists of a whole and its members Members may change, but the whole retains its identity A weak association Copyright © 2020 Pearson Education Ltd. Composition The whole has a responsibility for the parts, and is a stronger relationship If the whole is deleted, all parts are deleted Copyright © 2020 Pearson Education Ltd. Figure 10.19 An Example of Whole-Part and Aggregation Relationships Copyright © 2020 Pearson Education Ltd. Generalization/Specialization Diagrams Generalization Inheritance Polymorphism Abstract classes Messages Copyright © 2020 Pearson Education Ltd. Generalization Describes a relationship between a general kind of thing and a more specific kind of thing Described as an “is a” relationship Used for modeling class inheritance and specialization General class is a parent, base, or superclass Specialized class is a child, derived, or subclass Copyright © 2020 Pearson Education Ltd. Inheritance (2 of 2) Helps to foster reuse Helps to maintain existing program code Copyright © 2020 Pearson Education Ltd. Polymorphism The capability of an object-oriented program to have several versions of the same method with the same name within a superclass/subclass relationship The subclass method overrides the superclass method When attributes or methods are defined more than once, the most specific one is used Copyright © 2020 Pearson Education Ltd. Abstract Classes (2 of 2) Abstract classes are general classes No direct objects or class instances, and is only used in conjunction with specialized classes Usually have attributes and may have a few methods Copyright © 2020 Pearson Education Ltd. Figure 10.20 A Generalization/Specification Diagram is a Refined Form of a Class Diagram Copyright © 2020 Pearson Education Ltd. Finding Classes During interviewing or JAD sessions During facilitated team sessions During brainstorming sessions Analyzing documents and memos Examining use cases, looking for nouns Copyright © 2020 Pearson Education Ltd. Determining Class Methods Standard methods Examine a CRUD matrix Copyright © 2020 Pearson Education Ltd. Messages Used to send information by an object in one class to an object in another class Acts as a command, telling the receiving class to do something Consists of the name of the method in the receiving class, as well as the attributes that are passed with the method name May be thought of as an output or an input Copyright © 2020 Pearson Education Ltd. Statechart Diagrams (1 of 2) Used to examine the different states that an object may have Created for a single class – Objects are created, go through changes, and are deleted or removed Objects States Events – Signals or asynchronous messages – Synchronous – Temporal events Copyright © 2020 Pearson Education Ltd. Statechart Diagrams (2 of 2) Created when: – A class has a complex life cycle – An instance of a class may update its attributes in a number of ways through the life cycle – A class has an operational life cycle – Two classes depend on each other – The object’s current behavior depends on what happened previously Copyright © 2020 Pearson Education Ltd. Figure 10.22 A Statechart Diagram Showing How a Student Progresses from a Potential Student to a Graduated Student Copyright © 2020 Pearson Education Ltd. Packages Containers for other UML things Show system partitioning Can be component packages Can be physical subsystems Use a folder symbol May have relationships Copyright © 2020 Pearson Education Ltd. Figure 10.23 Use Cases Can Be Grouped into Packages Copyright © 2020 Pearson Education Ltd. Putting UML to Work The steps used in UML are: – Define the use case model – Continue UML diagramming to model the system during the systems analysis phase – Develop the class diagrams – Draw statechart diagrams – Begin systems design by refining the UML diagrams – Document your system design in detail Copyright © 2020 Pearson Education Ltd. Summary (1 of 2) Object-oriented systems – Objects – Classes – Inheritance CRC cards UML and use case modeling Components of UML – Things – Relationships – Diagrams Copyright © 2020 Pearson Education Ltd. Summary (2 of 2) UML diagrams – Use case diagrams – Activity diagrams – Sequence diagrams – Communication diagrams – Class diagrams – Statechart diagrams Using UML Copyright © 2020 Pearson Education Ltd.