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1 CS 501 Spring 2002
CS 501: Software Engineering
Lecture 16
Object Oriented Design I
2 CS 501 Spring 2002
Administration
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The Waterfall Model
Requirements Analysis
System design
Unit & Integration Testing
System Testing
Operation & Maintenance
Program design
Coding
Acceptance Testing
Requirements
Design
Implementation
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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
5 CS 501 Spring 2002
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
7 CS 501 Spring 2002
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
originsize
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
HelloWorld
paint()
class
name
operations
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Notation: Grouping and Annotation
A package is a general-purpose mechanism for organizing elements into groups.
Business rules
return copy of self
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
HelloWorld
paint() g.drawString ("HelloWorld", 0, 10)"
class
name
operations
annotation
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Class Diagram
Applet
HelloWorld
paint() Graphics
generalization
dependency
Note that the Applet and Graphics classes are shown elided.
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Class Inheritance Diagram
Object
Component
Container
Panel
Applet
HelloWorld
ImageObserver
interface
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Packaging Classes
applet
awt
lang
HelloWorld
java
Graphics
package
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Notation for Classes and Objects
Classes Objects
AnyClass
attribute1attribute2
operation1()operation2()
AnyClass
or
anObject:AnyClass
:AnyClass
anObject
The names of objects are underlined.
or
or
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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
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.
ISpelling
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Notation: Collaboration & Use Case
Place order
A use case is a description of a set of sequence of actions that a system performs that yields an observable result.
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.
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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
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
Parking Space
location
is_available()
1
0 ... 1
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Notation: Relationships (continued)
A generalization is a specialization/generalization relationship is which objects of the specialized element (child) are substitutable for objects of the generalized element (parent).
child parent
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
BookBorrower
libMem: LibraryMember
theCopy:Copy
theBook:Book
borrow(theCopy)okToBorrow
borrowborrow
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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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