UML

1
UML

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

2
Outline

• Introduction to UML
• Objects and Classes
• Class Diagrams
• Class Icon
• Relationships
• Constraints

3
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)

4
Objects and Classes

• Whats object
• Identity
• State
• Behavior
• Sequence Diagram
• Statechart Diagram
• Messages and methods
• Whats class
• Objects and Classes
• Nature of a class
• Class Attributes
• Operation (Method)
• Interfaces
• Interfaces and Implementation
• Corresponding C code

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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 a query action
• The structure and behaviour of similar objects
  are defined in their common class
• Objects have thee properties identity , state,
  and behaviour (query action)

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Object Property 1 Identity

• Identity is that property of an object which
  distinguishes it from all other 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"

7
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

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Object Property 3 Behaviour

• Behaviour is how an object acts and reacts, in
  terms of its status changes and
  message/information passing
• The state of an object represents the cumulative
  results of its behaviour

9
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)

10

• 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

11
Objects versus Classes

• 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

12
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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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

14

• In a 2D drawing package, circles have a radius, a
  line thickness, a line color, and a fill color
• 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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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

21
Class Icon

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

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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
• 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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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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• (Class Name, attribute, method) vs (Table Name,
  field, query)
• (Class object) vs (Table row)
• (Table 1, table 2, ) vs Knowledge relearning
  with OO techniques to quickly locate the
  information

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Design

• Organize the data into something (i.e.,
  object) being queried.
• Observe the relationship between objects.
• Describe the queries into methods, changing,
  updating, and even deleting the attribute
  information.
• If necessary, translate class, object, attribute
  value, and method to table, row, field value, and
  query.