OO programming and UML Design

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OO programming and UML Design

• Dr. Zhen Jiang
• West Chester University
• E-mail zjiang_at_wcupa.edu

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Outline

• Introduction to object and class
• Introduction to UML
• Introduction to UML design

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Introduction to object and class

• Whats object
• Identity
• State
• Behavior
• Sequence Diagram
• Statechart Diagram
• Messages and methods
• Whats class
• Objects and Classes
• Class Attributes
• Operation (Method)
• Interfaces
• Interfaces and Implementation

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Whats object

• Fundamentals of Object-Oriented Programming

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Whats object

• Conceptually, there are many ways to think of an
  object
• something that can be seen or touched
• a thing to which some action is directed
• something that performs an action
• The structure and behaviour of similar objects
  are defined in their common class
• Objects have three properties identity , state,
  and behaviour

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Object Property 1 Identity

• Identity is that property of an object which
  distinguishes it from all other objects
• Most programming languages use variable names to
  refer to objects
• Keep in mind, however, that an object may not
  have a name Similarly, an object might have
  multiple names (aliases)
• For this reason, there is a subtle distinction
  made between the concepts of "name" and "identity"

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Object Property 2 State

• The state of an object encompasses all of the
  descriptions of the object plus the current
  values of each of these descriptions

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Object Property 3 Behaviour

• Behaviour is how an object acts and reacts, in
  terms of its state changes and message passing
• The state of an object represents the cumulative
  results of its behaviour
• In object-oriented programming, a behaviour is
  invoked by sending a message to an object

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Sequence Diagrams

• A sequence diagram is an interaction diagram that
  focuses on the time ordering of messages
• A vertical dashed line is used to represent the
  lifetime of an object (its the objects
  lifeline)
• A focus of control is a tall, thin rectangle that
  shows the period of time during which an object
  is performing an action

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ATC
Radar
Pilot
requestLdgClearance(r)
checkWeather
checkRunwayClear(r)
clear
clearance
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Sequence
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Statechart Diagram

• Captures dynamic behavior (event-oriented)
• Purpose
• Model object lifecycle
• Model reactive objects (user interfaces, devices,
  etc.)

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Example Objects

• There are many physical objects we can examine
  right in this room
• each person is an object
• any chair is not an object
• each light bulb is an object
• Any book is not an object
• this room itself is an object (full or not)

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• See if the followings are objects or not
• Desk
• Lamp
• Person
• Log
• The Earth
• Clock
• Machine
• Computer
• Saving account
• Answer N, Y, Y, N, Y, Y, Y, Y, Y

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Messages and Methods

• A object executes a method when it sends/receives
  a message
• For example, we can ask/tell a dog to sit by
  sending him the message "sit"
• In object-oriented programming, objects send
  messages asking/telling others to perform
  behaviours -- those other objects invoke the
  method corresponding to the message in order to
  execute the desired behaviour

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Whats class

• A class describes the common structure
  (attributes/state) and behaviour of its instances
• For example,
• 3.14, 2.71, and 5.5 can be classified as Floats
• the following shapes can be classified as Circles

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Classes and Objects

• An object is called an "instance" of a class
• The terms instance and object are interchangeable
• Creating an object from a class is often called
  instantiation
• For example, there are many person objects in
  this room -- each person is an instance of the
  person class

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Classes and objects

• How would we describe the state, behaviour, and
  identity for each of these objects
• We have looked at objects and we have seen that
  objects can be "classified" into classes
• As programmers, we work with both classes and
  objects from those classes
• For example, we might write a stack class and
  create multiple stack objects for use in our
  program

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• In a 2D drawing package, circles have a radius, a
  line thickness, a line colour, and a fill colour
• Each individual circle (instance) drawn by the
  user has its own value for each attribute
• The programmer writes a Circle class and the
  program instantiates a Circle object every time
  the user draws a Circle

a snowman made from 9 Circle instances
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Class Attributes

• An attribute is a named property of a class that
  describes the range of values that instances of
  the property may hold.(Booch,1999)
• An attribute has a type that defines the type of
  its instances.
• Only the object itself should be able to change
  the value of its attributes.
• The values of the attributes define the state of
  the object

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Operation (Methods)

• An operation is the implementation of a service
  that can be requested from any object of the
  class to affect behavior (Booch, 1999)
• An operation can be
• Question (does not change the value of the
  object)
• Command (may change the value of the object)

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Interfaces

• An interface is a collection of operations that
  are used to specify a service of a class or a
  component (Booch, 1999)
• An interface is a contract of related services
  and a set of conditions that must be true for the
  contract to be faithfully executed
• Interfaces formalize polymorphism, they allow us
  to define polymorphism in a declarative way
  unrelated to implementation

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Interface and Implementation

• The class interface is its external (public) view
  
• The class implementation is its internal
  (private) view
• It is convenient to think of the interface as
  describing "what the objects of this class can
  do" and the implementation as "how the objects of
  this class do it"
• The implementation of a class consists of all the
  "behind the scenes" operations defined in the
  interface of the class

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Introduction to UML

• Whats UML
• Goals of UML
• Overview
• Class diagram
• Introduction
• Class icon
• Class relationship
• Constraints
• Other diagrams

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UML Unified Modeling Language

• The Unified Modeling Language (UML) is an
  industry-standard language for specifying,
  visualizing, constructing, and documenting the
  artifacts of software systems
• The UML definition was led by Grady Booch, Ivar
  Jacobson, and Jim Rumbaugh (all now at Rational
  Software)

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• UML simplifies the process of software design,
  making a "blueprint" for construction

In Essence a tool used through the analysis and
design phases of system development for
expressing the constructs and relationships of
complex systems
Target Usage for building object-oriented and
component-based systems
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Goals of UML
1. Provide users with a ready-to-use, expressive
visual modeling language so they can develop and
exchange meaningful models 2. Provide
extensibility and specialization mechanisms to
extend the core concepts. 3. Be independent of
particular programming languages and development
processes. 4. Provide a formal basis for
understanding the modeling language. 5.
Encourage the growth of the Object-Oriented tools
market. 6. Support higher-level development
concepts such as collaborations, frameworks,
patterns and components. 7. Integrate best
practices.
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• Many free learning materials on the web
• e.g. www.rational.com/uml
• Standard of UML
• www.cs.wcupa.edu/zjiang/01-09-67.pdf
• Some recommended texts on UML
• The Unified Modeling Language User Guide, G.
  Booch, J. Rumbaugh, I. Jacobson, 2000
• UML Explained, Kendall Scott, 2001
• Applying UML and Patterns 2nd Ed., Craig Larman,
  2002
• UML Distilled 2nd Ed., Martin Fowler with K.
  Scott, 2000
• UML and C, R. Lee W. Tepfenhart, 2001

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UML Overview

• UML is a language for visualizing, specifying,
  constructing and documenting the artifacts of a
  software system
• The artifacts might include requirements,
  architecture, design, source code, project plans,
  tests, prototypes, releases

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Review
something
Object
action
action
state1
state2
operations/methods
attributes attribute1,
attribute2
structure
operation/method
attribute1
attribute2
value
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Light
Turn on/off
On
Off
operations/methods
Turn_on/off ( )
attributes True, False
structure
Turn_on
True
False
value
Turn_off
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Class Diagram

• Introduction
• Class Icon
• Relationships
• Constraints

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Introduction

• The class diagram is fundamental to
  object-oriented programming
• UMLs class diagrams capture the attributes and
  operations of each class as well the
  relationships that exist between classes

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Class Icon

• Class Icon
• Hiding Details
• Visibility Notation
• Attribute Specification
• Operation Specification

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Class Icon

• The UML class icon is a rectangle with three
  compartments
• class name
• class attributes
• class operations
• Attributes are specified in the following form
• objectclass name

Circle
radius float center_x int center_y int
area() display()
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Hiding Detail

• You can optionally leave out the attributes,
  operations, or both in a class icon

Circle

area() display()
Circle
radius float center_x int center_y int
Circle
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UML Member Visibility Notation

• UML has three visibility prefixes for members
  for public, for protected, and for private
• e.g.

Circle
-radius float
area() display()
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Full UML Attribute Specification

• The full form of a UML attribute is as
  followsvisibility name multiplicity
  type initial value property
• The property choices are changeable, addOnly, and
  frozen

Student Info
-id string -hasGraduated bool false
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Full UML Operation Specification

• The full form of a UML operation is as
  followsvisibility name (parameter-list)
  return-type property
• The property choices are sequential, concurrent,
  guarded, and isQuery
• The full form of a UML parameter isdirection
  name type default-value
• The direction choices are in, out, and inout

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UML Class Relationships

• A class relationship is a connection between two
  (or more) classes
• The three most important class relationships are
  generalizations, associations, and aggregations
• UML provides a graphical representation for each
  of the relationships using a different line type
  for each relationship

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Class Relationships

• Generalization
• Association
• Association Class
• Qualified Association
• Ternary Association
• Aggregation

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Generalization

• A generalization is a relationship between a
  general thing (superclass) and a more specific
  kind of that thing (subclass)
• In the UML, generalization requires that objects
  of the subclass may be used anywhere an object of
  the superclass appears

Person
Student
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Association

• An association is a structural relationship that
  specifies that objects of one thing are connected
  to objects of another

Faculty
Student
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Association

• Associations can be adorned with a name.

Teaching
Faculty
Student
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Association

• Associations can be adorned with the roles.

teacher
Faculty
Student
learner
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Association

• Associations can be adorned with the
  multiplicity.

Faculty
Student
4..
1
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Association Class (relation attributes)

• Each object of association class is one instance
  of relationship (link) in an association.

1..
Faculty
Student
4..
Course
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Qualified Association

• Qualified association relates two classes and a
  qualifier.
• The qualifier is a special attribute that reduces
  the effective multiplicity of an association.

Directory
File
file name
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Ternary Association

• A ternary association is a structural
  relationship that specifies that objects of one
  thing are connected to objects of other twos.

Language
Project
Developer
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Aggregation

• An aggregation is an association that represents
  whole/part relationship
• The whole end of the association relationship
  is adorned with an open diamond shape (e.g. X is
  part of Y)
• e.g. doorDoor is part of carCar

X
Y
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Generalization, Aggregation, and Association

• See if the following pairs of classes have
  generalization, aggregation or association
• Faculty student (as)
• Hospital doctor (as)
• Door Car (ag --ltgt)
• Member Organization (ag --ltgt)
• People student (ge lt-- )
• Circle point (ge --gt)
• Department Faculty (as)
• Employee Faculty (ge lt--)
• Item Printer (ge lt--)
• Account Checking account (ge lt-- )

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Constraints

• Constraints on Object
• Constraints on Relations (Ordering)
• General Constraints (Dependency)

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UML class diagram is not object diagram
Customer
Loan
Bank
Bank-Loan
Other-Loan
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Constraints on Object

• The constraints restricts the values that objects
  can be.
• Example No employees salary can exceed the
  salary of the employees boss.

salary ltboss.salary
Employee Salary
Employer Salary
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Constraints on Relations (Ordering)

• Order indicates that the elements of the many
  end of an association have an explicit order that
  must be preserved.

ordered
Paper
Author
1
1..
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General Constraints (Dependency)

• A dependency is a using relationship that states
  that a change in specification of one thing may
  affect another thing that uses it (but not
  necessarily the reverse)

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General Constraints (Dependency)

• Dependencies are often used when one class uses
  another class as an argument of the operation
• Dependencies are also often used to express
  general constraints.

Aerodrome
checkRVR( r Runway )
Runway
member-of
Person
Committee
subset
chair-of
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UML Design

• UML class diagram is not object diagram.
• How to describe the behaviors/actions of objects
  in UML class diagram?
• UML class diagram is not data flow chart.
• What kind of relationship is generalization?
• How to keep the consistency of all the
  constraints?

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UML class diagram is not object diagram

• Should we add relation between Bank and
  Other-Loans?
• Can Bank change Other-loans?
• Instance of Loan and Other-Loans?

Other-Loan
Customer
Bank
Loan
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How to describe the behaviors/actions of objects
in UML class diagram
?
Person
Based on Use Case analysis
sSN address email
Student
Casher
Faculty
Customer
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How to describe the behaviors/actions of objects
in UML class diagram

• Use case (stories) Each use case defines an
  interaction between an actor and the system

Use case
Use case
System
Use case
Use case
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Reception

• Scenarios of a use case

Check
?
Order
Waiting
Failure
Authorized
Success
Failure
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How to describe the behaviors/actions of objects
in UML class diagram

• Basic idea
• behaviors interface
• For details, see in www.cs.wcupa.edu/zjiang/int
  ro_uc.ppt.

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UML class diagram is not data flow chart
bargain
Customer
Dealer
sign
buy
sell
report
Product
Manager
authorize
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UML class diagram is not data flow chart

• Customer, Dealer, and Manager
• Bargain

Product
Customer
Salesman
Dealer
Manager
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What kind of relationship is generalization
x int y int
Position
Point
Position
Point
People
?
Student
radius double
Rectangle
Circle
Tip 4 Class A is a super class of class B if
and only if any object of class B can also play
the role as an object of class A.
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How to keep the consistency of all the constraints
1
1..6
Ticket-buyer
Traveler
1
1
0..6
Dependent
1
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How to keep the consistency of all the constraints
0..1
0..1
Ticket-buyer
Traveler
1
1
0..6
Dependent
0..1
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How to keep the consistency of all the constraints
Traveler
0..1
1
0..6
Ticket-buyer
Dependent