UML and Patterns

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)

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

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

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.

Goals of UML


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 2
nd

Ed.
, [Craig Larman,
2002]

–
UML Distilled 2
nd

Ed.
, [Martin Fowler with K. Scott,
2000]

–
UML and C++
, [R. Lee & W. Tepfenhart, 2001]



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


Six diagram types will be introduced: class,
relationship, constraint, activity, sequence,
statechart

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:

–
Desk

–
Light

–
Person

–
Log

–
The Earth

–
Clock

–
Machine

–
Computer

–
Saving account


Answer: N, Y, Y, N, Y, Y, 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


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

Class Attributes

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

Object

something

action

state1

state2

action

attribute1

attribute2

operation/method

attributes: {attribute1,


attribute2}

operations/methods

value

structure

Review

Light

On

Off

Turn on/off

True

False

Turn_on

attributes: {True,


False}

operations/methods:

value

structure

Turn_off

Turn_on/off ( )

Class Diagram


Introduction


Class Icon


Relationships


Constraints




A game to demonstrate the use of class
diagram


Find your partner


Ask your partner to leave temporarily

–
Look at this picture carefully

–
You need to identify it from VERY similar
pictures in the next slide



–
Which one is shown before?







–
In the next slide, your partner will see the

–
Write down something to help your partner
to pick up the same picture correctly.



–
Quite, your partner’s job to pick up the
selected picture!


–
Which one?


Introduction


The class diagram is fundamental to object
-
oriented 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

Circle

area()

display()

Circle

radius: float

center_x: int

center_y: int


Circle

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


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
.

Faculty

Student

Teaching

Association


Associations can be adorned with the
roles
.

teacher

Faculty

Student

learner

Association


Associations can be adorned with
the multiplicity
.

4..*

Faculty

Student

1

Association Class (relation
attributes)

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

1..*

Faculty

Student

4..*

Course

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

Ternary Association


A ternary association is a structural relationship that
specifies that objects of one thing are
connected

to
objects of other two’s.

Developer

Language

Project

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.


Employee

Salary

Employer

Salary

{salary <=boss.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)

Aerodrome

checkRVR( r: Runway )

Runway


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.

Person

Committee

member
-
of

chair
-
of

{subset}

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 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

Customer

Bank

Loan

Other
-
Loan

•
Should we add relation
between Bank and Other
-
Loans?

•
Can Bank change Other
-
loans?

•
Instance of Loan and Other
-
Loans?

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

Faculty

Student

Customer

Casher

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

Customer

Dealer

Product

Manager

buy

sell

report

bargain

authorize

sign

UML class diagram is not data
flow chart

Customer

Dealer

Product

Manager

Salesman

•
Customer, Dealer, and Manager

•
Bargain


What kind of relationship is
generalization

People

Student

x: int

y: int

radius: double

Rectangle

Position

Point

Circle

Position

Point

*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

Dependent

Traveler

0..6

1

1

1..6

1

1

How to keep the consistency of
all the constraints

Ticket
-
buyer

Dependent

Traveler

0..6

1

0..1

0..1

0..1

1

How to keep the consistency of
all the constraints

Ticket
-
buyer

Dependent

Traveler

1

0..6

0..1