UML and Patterns
Dr. Zhen Jiang
West Chester University
E-mail: zjiang@wcupa.edu
url: www.cs.wcupa.edu/~zjiang
Outline

Introduction to UML
 Objects and Classes
 Class Diagrams
– Class Icon
– Relationships
– Constraints
Introduction to UML

What’s UML
 Goals of UML
 Overview
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)
UML simplifies
the process of software
design, making a "blueprint" for construction
Target Usage: for building object-oriented and
component-based systems
In Essence: a tool used through the analysis and design
phases of system development for expressing the
constructs and relationships of complex systems
Or
in a simple word:
Target on: class components
In Essence: analysis and design of relations (among
components)
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]
UML Overview

What is the target of UML, class?
Objects and Classes

What’s object
– Identity
– State
– Behavior


Sequence Diagram
Statechart Diagram

Messages and methods
 What’s class
–
–
–
–
–
–
–
Objects and Classes
Nature of a class
Class Attributes
Operation (Method)
Interfaces
Interfaces and Implementation
Corresponding C++ code
Objects and Classes

Fundamentals of Object-Oriented
Programming
Objects

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 thee properties: identity , state,
and behaviour
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"
Object Property 2: State

The state of an object encompasses all of the
(usually static) properties of the object plus
the current (usually dynamic) values of each
of these properties
Object Property 3: Behaviour

Behavior is how an object acts and reacts, in
terms of its state changes
 The state of an object represents the
cumulative results of its behavior
 In object-oriented programming, a behavior
is invoked by an interaction to this object
 If the receiver object does not have a
method for that message, an error is reported
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)

See if the followings are objects or not, in a system to
handle our CST class:
–
–
–
–
–
–
–
–

Desk
Light
Person
Log
The Earth
Clock
Computer
Saving account
Answer: N, Y, Y, N, N, Y, Y, Y
Objects versus Classes

How would we describe the state, behaviour,
and identity for each of these objects
 We have looked at rows as objects and we
have seen that objects can be "classified"
into a table, i.e., class.
 As programmers, we work with both classes
and objects
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
The Nature of a 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

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
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
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 in database can be:
– Creation (or adding a new one)
– Search & read
– Write / update
– Closing / deletion
Review
something
Object
action
state1
action
state2
operations/methods
attributes: {attribute1,
attribute2}
structure
operation/method
attribute1
attribute2
value
Light
Turn on/off
On
Off
operations/methods:
Turn_on/off ( )
attributes: {True,
False}
structure
Turn_on
True
False
Turn_off
value
UML Class Diagram

Introduction
 Class Icon
 Relationships
 Constraints
Introduction

The class diagram is fundamental to objectoriented programming
 UML’s class diagrams capture the attributes
and operations of each class as well the
relationships (information ownership) that
exist between classes
Class Icon





Class Icon
Hiding Details
Visibility Notation
Attribute Specification
Operation Specification
UML 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:
– object:class name
Circle
radius: float
center_x: int
center_y: int
area()
display()
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
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
Class Relationships

Generalization
 Association
 Association Class
 Qualified Association
 Ternary Association
 Aggregation
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
Association
An
association is a structural relationship that specifies
that objects of one thing are connected to objects of
another
Faculty
Student
Association
Associations
can be adorned with a name.
Teaching
Faculty
Student
Association
Associations
Faculty
can be adorned with the roles.
teacher
learner
Student
Association
Associations
Faculty
can be adorned with the multiplicity.
1
4..*
Student
Association Class (relation
attributes)

Each object of association class is one
instance of relationship (link) in an
association.
Faculty
1..*
4..*
Course
Student
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
name
File
Ternary Association

A ternary association is a structural relationship that
specifies that objects of one thing are connected to
objects of other two’s.
Project
Language
Developer
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. door:Door is part of car:Car
X
Y
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 --<>)
 Member & Organization (ag --<>)
 People & student (ge <|-- )
 Circle & point (ge --|>)
 Department & Faculty (as)
 Employee & Faculty (ge <|--)
 Item & Printer (ge <|--)
 Account & Checking account (ge <|-- )
Constraints

Constraints on Object
 Constraints on Relations (Ordering)
 General Constraints (Dependency)
Constraints on Object
The
constraints restricts the values that
objects can be.
Example:
No employee’s salary can exceed
the salary of the employee’s boss.
{salary <=boss.salary}
Employee
Salary
Employer
Salary
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)
General Constraints
(Dependency)

Dependencies are often used when one class uses
another class as an argument of the operation
Aerodrome
checkRVR( r: Runway )

Runway
Dependencies are also often used to express general
constraints.
member-of
Person
{subset}
chair-of
Committee
Design
•
•
•
•
Organize the data into “something” (i.e.,
object) being queried.
Observe the relationship between
objects.
Describe the queries into methods,
updating, and even deleting the attribute
information.
At the end, translate class, object,
attribute value, and method to table, row,
field value, and query, resepctively.
For example, this CST class!
•
•
•
•
•
•
What you think important?
What are objects?
What are relations?
Class?
TA?
Attributes, and methods?
Mischief

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?
UML class diagram is not object
diagram
Other-Loan
Customer
Bank
Loan
•Should we add relation
between Bank and OtherLoans?
•Can Bank change Otherloans?
•Instance of Loan and OtherLoans?
UML class diagram is not object
diagram
Customer
Bank
Loan
Bank-Loan
Other-Loan
How to describe the
behaviors/actions of objects in
UML class diagram
Person
sSN
address
?
email
Customer
Faculty
Casher
Student
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)
UML class diagram is not data
flow chart
bargain
Customer
Dealer
sign
buy
Product
sell
authorize
report
Manager
UML class diagram is not data
flow chart
•Customer, Dealer, and Manager
•Bargain
Product
Customer
Salesman
Dealer
Manager
What kind of relationship is
generalization
Position
Point
x: int
y: int
People
Student
Circle
radius: double
Point
Position
Rectangle
*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.
How to keep the consistency of
all the constraints
Ticket-buyer
1
Traveler
1
1
0..6
Dependent
1..6
1
How to keep the consistency of
all the constraints
Ticket-buyer
0..1
Traveler
1
1
0..6
Dependent
0..1
0..1
How to keep the consistency of
all the constraints
Traveler
0..1
Ticket-buyer
1
0..6
Dependent