Chapter 22 Object-Oriented Systems Analysis and Design and UML Systems Analysis and Design Kendall and Kendall Fifth Edition

Chapter 22Object-Oriented SystemsAnalysis and Design and UML

Systems Analysis and DesignKendall and Kendall

Fifth Edition

Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-2

Major Topics

Object-oriented programming concepts

Object-oriented terminology Five-layer model CRC Cards Unified Modeling Language Use case and other UML diagrams Relationships


Object-Oriented Overview

Object-oriented techniques work well in situations where complicated systems are undergoing continuous maintenance, adaptation, and design

There are two ways to model object-oriented systems Coad and Yourdon methodology The Unified Modeling Language


Object-Oriented Programming

Six ideas characterize object-oriented programming: An object, which represents a real-

world thing or event A class, or group of related objects Messages, sent between objects Encapsulation, only an object makes

changes through its own behavior


Object-Oriented Programming

Six ideas characterize object-oriented programming (continued): Inheritance, a new class created from

another class Polymorphism, meaning that a

derived class behavior may be different from the base class


Terminology

Class refers to a template for a group of individual objects with common attributes and common behavior

The difference between an Object and a Class is that the class defines shared attributes and behaviors of objects

An object is an instance or occurrence of a class


Terminology

Another name for property is attribute

Another name for method is operation

Interface means the behavior of a class or component that is noticeable from outside the class or component


Encapsulation

Encapsulation changes the manner in which data is updated by programs because data can only be changed via the services that encapsulate the data


Inheritance

The two types of classes are involved in any inheritance relationship are the base class and the derived class

Multiple inheritance means there will be multiple occurrences of the base type of class in the inheritance relationship

Polymorphism only occurs where there is inheritance


Five-Layer Model

Object oriented analysis and design is based on a five-layer model: Class/object layer notes the classes and

objects Structure layer captures various structures

of classes and objects, such as one-to-many relationships and inheritance

Attribute layer details the attributes of classes


Five-Layer Model

Five-layer model, continued Service layer notes messages and

object behaviors Subject layer divides the design into

implementation units or team assignments


Five General Types of Objects

There are five general types of objects: Tangible things Roles Incidents Interactions Specifications details


Criteria to Determine Need for a New Class of Objects

Criteria to determine whether a new class of objects is justified There is a need to remember the object There is a need for certain behaviors of

the object An object has multiple attributes A class has more than one object

instantiation Unless it is a base class



Criteria, continued Attributes have a meaningful value

for each object in a class Services behave the same for every

object in a class Objects implement requirements that

are derived from the problem setting



Criteria, continued Objects do not duplicate attributes

and services that could be derived from other objects in the system


Basic Types of Structures

There are two basic types of structures that might be imposed on classes and objects: Generalization-Specialization structure

(Gen-Spec), which connect class-to-class

Whole-Part structure which are collections of different objects that compose another whole object


Instance Connections

Instance connections are references between objects such as associations or relationships indicated by a single line between objects using the same cardinality notation as Whole-Part structures


Methods

Services (or methods or procedures) must be analyzed. Activities are Object state analysis, showing changes

of state Service specification: creating, storing,

retrieving, connecting, accessing, and deleting objects

Message specification, consisting of control and data flow


Major Components of Object-Oriented Design Activities

Object-oriented design activities are grouped into four major components: The problem domain component The human interface component The data management component The task management component


Problem Domain Component

The problem domain component consists of Reuse design Implementation structures Language accommodation


CRC Cards

Class, responsibilities, and collaborators (CRC) cards are used to represent the responsibilities of classes and the interaction between the classes


Creating CRC Cards

Analysts create CRC cards by Finding all the nouns and verbs in a

problem statement Create scenarios that are actually

walkthroughs of system functions Identify and refine responsibilities into

smaller and smaller tasks, if possible


Creating CRC Cards

Creating CRC cards, continued The group determines how tasks are

fulfilled by objects or interacting with other things

Responsibilities evolve into methods or operations


The Unified Modeling Language (UML)

UML (Unified Modeling Language) is the result of a collaboration of individual object-oriented methods that has been adopted as a standard for modeling object-oriented systems

It differs from the Coad and Yourdon OOA-OOD in the way that it breaks down objects and their relationships


The Unified Modeling Language (UML)

UML has three categories: Things, the objects Relationships, the glue that holds

things together Diagrams, categorized as either

structure or behavioral


Use Case

A use case describes three things: An actor (user) that initiates an event An event that triggers a use case The use case that performs the

actions triggered by the event


Kinds of Use Cases

There are two kinds of use cases: Primary, the standard flow of events

within a system that describe a standard system behavior

Use case scenarios that describe variations of the primary use case


Steps for Creating a Use Case Model

The steps required to create a use case model are Review the business specifications

and identify the actors within the problem domain

Identify the high-level events and develop the primary use cases that describe the events and how actors initiate them


Steps for Creating a Use Case Model

Creating a use case model, continued Review each primary use case to

determine possible variations of flow through the use case

Develop the use case documents for all primary use cases and all important use case scenarios

Move to UML diagramming techniques to complete the systems analysis and design


Two General Groupings of Things

There are two general groupings of things in UML: Structural things that define the

conceptual and physical structures of an O-O system and are described by nouns

Behavioral things, the verbs of a UML model that represent the behavior of the system and the states of the system before, during, and after the behaviors occur


Categories of Structural Things

There are seven categories of structural things

The first five are conceptual or logical

The last two are physical in nature Component Node



Seven categories of structural things: Classes, which have properties or

attributes and methods or operations Interfaces, the behavior of a class or

component of a system that is noticeable from outside the class or component



Seven categories, continued Collaborations, which describe the

interactions of two or more things in a system that perform a behavior that is more than any one of the things can do alone

Use cases, which describe a series of actions that demonstrate a distinct behavior of the system and its interactions with the actors



Seven categories, continued Control or active classes

A control class can initiate and control an independent flow of activity within the system

Components, which are a physical part of a system that represents the services and interfaces implemented by the elements contained within that component, including software code



Seven categories, continued Nodes, which represent a piece of

hardware on which your system executes

Components are physically deployed on nodes


Behavioral Things

Behavioral things consist of Interactions, or messages sent

between a set of objects within the system to perform a specific task

State machine, a series of states that an object goes through in response to actions within the system


Packages

Packages are groups of things They can be physical subsystems


Types of Relationships

There are two types of relationships that hold things together: Structural Behavioral


Types of Structural Relationships

There are four types of structural relationships: Dependencies, where one thing affects

another thing that uses it Aggregations, which show how the

whole object is composed of the sum of its parts

Associations that describe structural connections between things


Types of Structural Relationships

Four types of structural relationships, continued Generalizations, which describe a

relationship between a general kind of thing and a more specific kind of thing, used for modeling class inheritance and specialization


Types of Active Behavioral Relationships

There are four active behavioral relationships: Communicates is used to connect an

actor to a use case Includes describes the situation

where a use case contains a behavior that is common to more than one use case


Types of Active Behavioral Relationships

Types of active behavioral relationships, continued Extends describes the situation where

one use case possesses the behavior that allows the new use case to handle a variation or exception

Generalizes implies that one thing is more typical than the other thing


UML Structural Diagrams

UML structural diagrams include Class diagrams used to model the

static structural design of a system Object diagrams portray the state of

class instances and their relationships at a point in time


UML Structural Diagrams

UML structural diagrams, continued Component diagrams show an

overview of the system architecture A deployment diagram illustrates the

physical implementation of the system, including the hardware


Behavioral Diagrams

Behavioral diagrams describe the interaction between people and a use case


Behavioral Diagrams

Behavioral Diagrams include Use case diagrams, showing the actors

and the use cases Sequence diagrams that depict a

succession of interactions between object instances over time and they show the processing described in use case scenarios

Activity diagrams show the flow of activities within a process


Behavioral Diagrams

Behavioral Diagrams, continued Collaboration diagrams illustrate a

sequence of object interactions showing the organization of the objects during the interactions

State chart diagrams show the states of an object and the events and conditions that trigger a transition from one state to another


Steps Used in UML

The steps used in UML are Define the use case model Define the object model Continue UML diagramming to model the

system during the systems analysis phase

Begin system design by refining UML diagrams and using them to derive classes and their properties and methods

Documents

Chapter 22 Object-Oriented Systems Analysis and Design and UML Systems Analysis and Design Kendall and Kendall Fifth Edition