CS 501: Software Engineering
Lecture 16
Object Oriented Design I
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Administration
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The Waterfall Model
Requirements
Requirements Analysis
System design
Design
Program design
Implementation
Coding
Unit & Integration Testing
System Testing
Acceptance Testing
Operation & Maintenance
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Program Design
The task of program design is to represent the software
system functions in a form that can be transformed into
one or more executable programs.
Given a system architecture, the program design specifies:
• computers and networks
• programs, components, packages, classes and class
hierarchies
• interfaces, protocols
• security mechanisms, operational procedures
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The Importance of Modeling
• A model is a simplification of reality.
• We build models so that we can better understand the
system we are developing.
• We build models of complex system because we cannot
comprehend such a system in its entirety.
Models can be informal or formal. The more complex the
project the more valuable a formal model becomes.
BRJ
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Principles of Modeling
• The choice of what models to create has a profound
influence on how a problem is attacked and how a
solution is shaped.
• Every model can be expressed at different levels of
precision.
• The best models are connected to reality.
• No single model is sufficient. Every nontrivial
system is best approached through a small set of
nearly independent models.
BRJ
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The Unified Modeling Language
UML is a standard language for modeling software systems
• Serves as a bridge between the requirements specification
and the implementation.
• Provides a means to specify and document the design of a
software system.
• Is process and programming language independent.
• Is particularly suited to object-oriented program
development.
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Useful Texts
Grady Booch, James Rumbaugh, Ivar Jacobson, The Unified
Modeling Language. Addison-Wesley 1999.
Grady Booch, Object-Oriented Analysis and Design with
Applications, second edition. Benjamin/Cummings 1994.
Rob Pooley, Perdita Stevens, Using UML Software
Engineering with Objects and Components. Addison-Wesley
1999.
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Rational Rose
Rational Rose is a system for creating and managing
UML diagrams.
It is available on all Computer Science Department
computers.
See: http://adm/Software/purify_install.htm for
installation instructions.
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Notation: Classes
Window
origin
size
open()
close()
move()
display()
name
attributes
operations
A class is a description of a set of objects that share the same
attributes, operations, relationships and semantics.
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The HelloWorld Example
class
name
HelloWorld
operations paint()
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Notation: Grouping and Annotation
Business rules
A package is a general-purpose mechanism for organizing
elements into groups.
return copy
of self
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A note is a symbol for rendering constraints and
comments attached to an element or a collection of
elements.
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Abstraction for HelloWorld
class
name
HelloWorld
annotation
operations paint()
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g.drawString
("HelloWorld", 0, 10)"
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Class Diagram
Applet
generalization
Note that the Applet
and Graphics classes
are shown elided.
HelloWorld
paint()
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dependency
Graphics
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Class Inheritance Diagram
Object
Panel
interface
Component
ImageObserver
Applet
Container
HelloWorld
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Packaging Classes
java
HelloWorld
applet
Graphics
awt
package
lang
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Notation for Classes and Objects
Classes
AnyClass
attribute1
attribute2
operation1()
operation2()
or
AnyClass
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Objects
anObject:AnyClass
or
:AnyClass
or
anObject
The names of objects are
underlined.
CS 501 Spring 2002
The "Hello, World" Implementation
import java.awt.Graphics;
class HelloWorld extends java.applet.Applet {
public void paint (Graphics g) {
g.drawString ("Hello, World!", 10, 10);
}
}
Example from: BJR
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Notation: Interface
ISpelling
An interface is a collection of operations that specify a
service of a class or component, i.e., the externally
visible behavior of that element.
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Notation: Collaboration & Use Case
Chain of
responsibility
A collaboration defines an interaction, i.e., a society of
roles and other elements that work together to provide some
cooperative behavior.
Place order
A use case is a description of a set of sequence of actions
that a system performs that yields an observable result.
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Notation: Active Class
EventManager
eventlist
suspend()
flush()
An active class is a class whose objects own one or
more processes or threads and therefore can initiate
control activity.
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Notation: Component & Node
orderform.java
A component is a physical and replaceable
part of a system that conforms to and provides
the realization of a set of interfaces.
Server
A node is a physical element that exists at run
time and represents a computational resource.
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Notation: Behavioral Things:
Messages & States
display
An interaction is a behavior that comprises a set of messages
exchanged among a set of objects within a particular context to
accomplish a specific purpose.
Waiting
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A state machine is a behavior that specifies the sequence of
states an object or an interaction goes through during its
lifetime in response to events.
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Notation: Relationships
A dependency is a semantic relationship between two things in
which a change to one may effect the semantics of the other.
0..1
employer
*
employee
An association is a structural relationship that describes
a set of links, a link being a connection among objects.
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Relationships
Parking
1
0 ... 1
Parking Space
location
is_available()
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Notation: Relationships (continued)
child
parent
A generalization is a specialization/generalization
relationship is which objects of the specialized
element (child) are substitutable for objects of the
generalized element (parent).
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A realization is a semantic relationship between
classifiers, wherein one classifier specifies a
contract that another classifier guarantees to carry
out.
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Diagrams in UML
A diagram is the graphical representation of a set of
elements, usually rendered as a connected graph of vertices
(things) and arcs (relationships).
• Class diagram shows a set of classes, interfaces, and
collaborations with their relationships.
• Object diagram shows a set of objects and their
relationships.
• Use case diagram shows a set of use cases and actors (a
special kind of class) and their relationships.
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Diagrams in UML (continued)
Interaction diagram shows an interaction, consisting of a
set of objects and the relationships, including the messages
that may be dispatched among them.
=> A sequence diagram emphasizes the time ordering.
=> A collaboration diagram emphasizes the structural
organization of the objects that send and receive
messages.
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Example: A Sequence Diagram
libMem:
LibraryMember
BookBorrower
theBook:Book
theCopy:Copy
borrow(theCopy)
okToBorrow
borrow
borrow
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Diagrams in UML (continued)
• Statechart diagram shows a state machine consisting
of states, transitions, events, and activities.
• Activity diagram is a statechart diagram that shows the
flow from activity to activity within a system.
• Component diagram shows the organization and
dependencies among a set of components.
• Deployment diagram shows the configuration of
processing nodes and the components that live on them.
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