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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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-3
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-4
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-5
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-6
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-7
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-8
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-9
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-10
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-11
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-12
Five General Types of Objects
There are five general types of objects: Tangible things Roles Incidents Interactions Specifications details
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-13
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-14
Criteria to Determine Need for a New Class of Objects
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-15
Criteria to Determine Need for a New Class of Objects
Criteria, continued Objects do not duplicate attributes
and services that could be derived from other objects in the system
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-16
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-17
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-18
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-19
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-20
Problem Domain Component
The problem domain component consists of Reuse design Implementation structures Language accommodation
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-21
CRC Cards
Class, responsibilities, and collaborators (CRC) cards are used to represent the responsibilities of classes and the interaction between the classes
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-22
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-23
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-24
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-25
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-26
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-27
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-28
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-29
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-30
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-31
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-32
Categories of Structural Things
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-33
Categories of Structural Things
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-34
Categories of Structural Things
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-35
Categories of Structural Things
Seven categories, continued Nodes, which represent a piece of
hardware on which your system executes
Components are physically deployed on nodes
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-36
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-37
Packages
Packages are groups of things They can be physical subsystems
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-38
Types of Relationships
There are two types of relationships that hold things together: Structural Behavioral
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-39
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-40
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-41
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-42
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-43
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-44
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-45
Behavioral Diagrams
Behavioral diagrams describe the interaction between people and a use case
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-46
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-47
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
Kendall & Kendall Copyright © 2002 by Prentice Hall, Inc. 22-48
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