Systems Analysis & Design
Tenth Edition
Chapter 10
Object-Oriented
•
Systems
Analysis and
Design Using
UML
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Learning Objectives (1 of 2)
• Understand what object-oriented systems
analysis and design is and appreciate its
usefulness
• Comprehend the concepts of Unified Modeling
Language (UML), the standard approach for
modeling a system in the object-oriented world
• Apply the steps used in UML to break down the
system into a use case model and then a class
model
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Learning Objectives (2 of 2)
• Diagram systems with the UML toolset so they
can be described and properly designed
• Document and communicate the newly modeled
object-oriented system to users and other
analysts
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Object-Oriented Analysis and
Design
• 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.
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Object-Oriented Analysis and
Design (continued)
• 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
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Major Topics
• Object-oriented concepts
• CRC cards and object think
• Unified Modeling Language
• Use case and other UML diagrams
• Packages
• Using UML
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Object-Oriented Concepts
• Objects
• Classes
• Inheritance
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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
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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
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Figure 10.1 An Example of a UML
Class:
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Inheritance
• 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
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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.
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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
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Figure 10.3 Four CRC Cards
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Interacting during a CRC Session
• Identify all the classes you can
• Create scenarios
• Identify and refine responsibilities
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The Unified Modeling Language
(UML) Concepts and Diagrams
• Things
• Relationships
• Diagrams
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Figure 10.4 An Overall View of UML and Its Components:
Things, Relationships, and Diagrams
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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
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Relationships
• Structural relationships
– Tie things together in structural diagrams
• Behavioral relationships
– Used in behavioral diagrams
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Structural Relationships
• Dependencies
• Aggregations
• Associations
• Generalizations
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Behavioral Relationships
• Communicates
• Includes
• Extends
• Generalizes
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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)
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Structural Diagrams
• Class diagrams
• Object diagrams
• Component diagrams
• Deployment diagrams
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Behavioral Diagrams
• Use case diagrams
• Sequence diagrams
• Collaboration or communication diagrams
• Statechart diagrams
• Activity diagrams
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Commonly Used UML Diagrams
• 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
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Commonly Used UML Diagrams
(continued)
• Sequence diagrams
– Show the sequence of activities and class
relationships
• Class diagrams
– Show classes and relationships
• Statechart diagrams
– Show the state transitions
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Figure 10.5 An Overview of UML Diagrams Showing How
Each Diagram Leads to the Development of Other UML
Diagrams
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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
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Figure 10.6 A Use Case Example of
Student Enrollment
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Figure 10.7 A Use Case Scenario Is Divided into Three
Sections: Identification and Initiation, Steps Performed,
and Conditions, Assumptions, and Questions
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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
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Figure 10.8 Specialized Symbols Are Used
to Draw an Activity Diagram
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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
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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
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Figure 10.9 This Activity Diagram Shows Three
Swimlanes: Client Web Page, Web Server, and Mainframe
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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
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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
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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
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• object Name: A name with a colon after it
represents an object.
• :class A colon with a name after it
represents a class.
• objectName:class A name, followed by a
colon and another name, represents an
object in a class.
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Figure 10.10 Specialized Symbols Used
to Draw a Sequence Diagram
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Figure 10.11 A Sequence Diagram for Student Admission:
Sequence Diagrams Emphasize the Time Ordering of
Messages
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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
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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.
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Copyright
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