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OO programming and UML OO programming and UML DesignDesign
Dr. Zhen Jiang
West Chester University
E-mail: [email protected]
OutlineOutline
Introduction to object and classIntroduction to UML Introduction to UML design
Introduction to object and classIntroduction to object and classWhy OO programming?
– Look at this picture carefully– You need to identify it from VERY similar
pictures in the next slide
Introduction to object and classIntroduction to object and classWhy OO programming?
– Which one is shown before?
– In the next slide, your partner will see the selected picture and other two pictures together. Write down something to help your partner to pick up the same picture correctly.
Introduction to object and classIntroduction to object and classWhy OO programming?
– Partner’s job
Introduction to object and classIntroduction to object and classWhy OO programming?
– Which one?
Introduction to object and classIntroduction to object and classWhy OO programming?
– From snapshot to the action
Introduction to object and classIntroduction to object and classWhy OO programming?
– From snapshot to the action
3
2
1
Introduction to object and classIntroduction to object and classWhat’s object
– Identity– State– Behavior
Sequence Diagram Statechart Diagram
– Messages and methodsWhat’s class
– Objects and Classes– Class Attributes– Operation (Method)– Interfaces– Interfaces and Implementation
What’s objectWhat’s object
Fundamentals of Object-Oriented Programming
What’s objectWhat’s objectConceptually, 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
Object Property 1: Object Property 1: IdentityIdentityIdentity is that property of an object which
distinguishes it from all other objectsMost programming languages use variable
names to refer to objectsKeep 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: StateObject Property 2: StateThe state of an object encompasses all of the
descriptions of the object plus the current values of each of these descriptions
Object Property 3: Object Property 3: BehaviourBehaviourBehaviour 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
Example ObjectsExample ObjectsThere 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– Lamp– Person– Log– The Earth– Clock– Machine– Computer– Saving account
Answer: N, Y, Y, N, Y, Y, Y, Y, Y
What’s the relationship among What’s the relationship among objects: Messages and Methodsobjects: 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 behaviors -- those other objects invoke the method corresponding to the message in order to execute the desired behavior
What’s classWhat’s classA class describes the common structure
(attributes/state) and behaviour of its instancesFor example,
– 3.14, 2.71, and 5.5 can be classified as Floats
– the following shapes can be classified as Circles
Classes and ObjectsClasses and ObjectsAn object is called an "instance" of a classThe terms instance and object are
interchangeableCreating an object from a class is often
called instantiationFor example, there are many person objects
in this room -- each person is an instance of the person class
Classes and objectsClasses and objectsHow 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
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
Simply, a class is a group of objects with common parts or behaviors (similar, not necessary the exact same). That common thing will be defined in class definition.
An object is an instance which meets all the description of its class.
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 AttributesClass Attributes
Operation (Methods)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)
Interface and ImplementationInterface and ImplementationThe class interface is its external (public)
view The class implementation is its internal
(private) viewIt 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
Introduction to UMLIntroduction to UML
What’s UML Goals of UML Overview
– Class diagram Introduction Class icon Class relationship Constraints
– Other diagrams
UML: Unified Modeling UML: Unified Modeling LanguageLanguage
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 UMLGoals of UML
Many free learning materials on the web– e.g. www.rational.com/uml
Standard of UMLwww.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 OverviewUML OverviewUML 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
Objectsomething
action
state1 state2action
attribute1 attribute2
operation/method
attributes: {attribute1, attribute2}
operations/methods
value
structure
ReviewReview
Light
On OffTurn on/off
True FalseTurn_on
attributes: {True, False}
operations/methods:
value
structure
Turn_off
Turn_on/off ( )
Class DiagramClass DiagramIntroductionClass IconRelationshipsConstraints
IntroductionIntroductionThe class diagram is fundamental to object-
oriented programmingUML’s class diagrams capture the attributes
and operations of each class as well the relationships that exist between classes
Class IconClass Icon Class Icon Hiding Details Visibility Notation Attribute Specification Operation Specification
Class IconClass 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 DetailHiding 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 Member Visibility UML Member Visibility NotationNotation
UML has three visibility prefixes for members:+ for public, # for protected, and – for private
–e.g.Circle
-radius: float
#area()
+display()
Full UML Attribute Full UML Attribute SpecificationSpecification
The full form of a UML attribute is as follows:[visibility] name [multiplicity] [: type] [= initial value] [{property}]
– The property choices are changeable, addOnly, and frozen
Student Info
-id: string
-hasGraduated: bool = false
Full UML Operation Full UML Operation SpecificationSpecification
The full form of a UML operation is as follows:[visibility] name [(parameter-list)] [:return-type] [{property}]
– The property choices are sequential, concurrent, guarded, and isQuery
The full form of a UML parameter is:[direction] name : type [= default-value]
– The direction choices are in, out, and inout
UML Class RelationshipsUML Class RelationshipsA class relationship is a connection between
two (or more) classesThe 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 RelationshipsClass RelationshipsGeneralizationAssociationAssociation ClassQualified AssociationTernary AssociationAggregation
GeneralizationGeneralization 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
AssociationAssociationAn association is a structural relationship that
specifies that objects of one thing are connected to objects of another
Faculty Student
AssociationAssociationAssociations can be adorned with a name.
Faculty StudentTeaching
AssociationAssociationAssociations can be adorned with the roles.
teacherFaculty Studentlearner
AssociationAssociationAssociations can be adorned with the multiplicity.
4..*Faculty Student
1
Association Class (relation Association Class (relation attributes)attributes)
Each object of association class is one instance of relationship (link) in an association.
1..*Faculty Student4..*
Course
Qualified AssociationQualified AssociationQualified association relates two classes and
a qualifier. The qualifier is a special attribute that
reduces the effective multiplicity of an association.
Directory Filefile name
Ternary AssociationTernary Association A ternary association is a structural relationship that
specifies that objects of one thing are connected to objects of other two’s.
Developer
LanguageProject
AggregationAggregationAn aggregation is an association that
represents whole/part relationshipThe “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 Generalization, Aggregation, and AssociationAssociation
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 <|-- )
ConstraintsConstraintsConstraints on ObjectConstraints on Relations (Ordering)General Constraints (Dependency)
Constraints on ObjectConstraints on ObjectThe 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}
Constraints on Relations Constraints on Relations (Ordering)(Ordering)
{Order} indicates that the elements of the “many” end of an association have an explicit order that must be preserved.
Paper Author{ordered}
11..*
General Constraints General Constraints (Dependency)(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 General Constraints (Dependency)(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 Committeemember-of
chair-of
{subset}
UML DesignUML DesignUML class diagram is not object diagram.UML class diagram is not data flow chart.How to describe the behaviors/actions of
objects in UML class diagram?What kind of relationship is generalization?How to keep the consistency of all the
constraints?Common mistakes in Time Sequence DiagramSamples
UML class diagram is not object UML class diagram is not object diagramdiagram
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 UML class diagram is not object diagramdiagram
Customer
Bank
Loan
Bank-Loan Other-Loan
UML class diagram is not data UML class diagram is not data flow chartflow chart
Customer Dealer
Product Manager
buy sell report
bargain
authorize
sign
UML class diagram is not data UML class diagram is not data flow chartflow chart
Customer
Dealer
Product
Manager
Salesman
•Customer, Dealer, and Manager•Bargain
How to describe the How to describe the behaviors/actions of objects in behaviors/actions of objects in
UML class diagramUML class diagram
?
Person
sSNaddressemail
Faculty StudentCustomer Casher
How to describe the How to describe the behaviors/actions of objects in behaviors/actions of objects in
UML class diagramUML class diagram
Use case (stories): Each use case defines an interaction between an actor and the system
Use case
Use case
Use case
Use case
Scenarios of a use case Reception
Check
Failure
Authorized
Waiting
Success Failure
?
Order
How to describe the How to describe the behaviors/actions of objects in behaviors/actions of objects in
UML class diagramUML class diagram
– In design, see www.cs.wcupa.edu/~zjiang/intro_uc.ppt.
– In programming, see time sequence diagram, see www.cs.wcupa.edu/~zjiang/intro_TS.ppt.
What kind of relationship is What kind of relationship is generalizationgeneralization
People
Student
x: inty: int
radius: doubleRectangle
PositionPoint
Circle
PositionPoint
*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 How to keep the consistency of all the constraintsall the constraints
Ticket-buyer
Dependent
Traveler
0..6
1
1 1..6
1
1
How to keep the consistency of How to keep the consistency of all the constraintsall the constraints
Ticket-buyer
Dependent
Traveler
0..6
1
0..1 0..1
0..1
1
How to keep the consistency of How to keep the consistency of all the constraintsall the constraints
Ticket-buyer Dependent
Traveler
1 0..60..1