Class DiagramClass Diagram

Class DiagramClass Diagram

A class diagram describes the classes and A class diagram describes the classes and the association (static relationship) the association (static relationship) between these classes ( between these classes ( 描述系統中物件描述系統中物件的的 type(class)type(class) ，以及這些，以及這些 class class 的的靜態關靜態關連連 .).)association (for example, a customer may association (for example, a customer may

rent a number of videos)rent a number of videos)subtypes ( a nurse is a kind of person)subtypes ( a nurse is a kind of person)

OrderdateReceived

isPrepaidnumber:stringprice:Money

dispatch()close

Order LineQuantity:integer

price:MoneyisSatisfied:bool

Customername

addresscreditRating():String

Corporatecustomer

contractNamecreditRatingcreditLimitremind()

billForMonth(int)

PersonalCustomer

CreditCard#

Employee

Product

* 1

1

*

1*

lineitems

{if Order.customer.creditRatingis “poor”, then Order.isPrepaidmust be true }

*0..1

{creditRating()=“poor”}sale rep

Multiplicity:mandatoryMultiplicity:many-valued

association

constraints

attributes generalizationclass

Multiplicty:optional

Rolename

navigabilitynavigability

See next figSee next fig In specification model, an Order has a In specification model, an Order has a

responsibility to tell you which Customer it responsibility to tell you which Customer it is for, but not converselyis for, but not conversely

In implementation diagram, this would In implementation diagram, this would indicate that Order contains a pointer to indicate that Order contains a pointer to CustomerCustomer

OrderdateReceived

isPrepaidnumber:stringprice:Money

dispatch()close

Order LineQuantity:integer

price:MoneyisSatisfied:bool

Customername

addresscreditRating():String

Corporatecustomer

contractNamecreditRatingcreditLimitremind()

billForMonth(int)

PersonalCustomer

CreditCard#

Employee

Product

* 1

1

*

1*

lineitems

{if Order.customer.creditRatingis “poor”, then Order.isPrepaidmust be true }

*0..1

{creditRating()=“poor”}sale rep

navigability

GeneralizationGeneralization

Generalization (In OOP term, is Generalization (In OOP term, is inheritance)inheritance)

see personal and corporate customerssee personal and corporate customersUsing polymorphism, the corporate Using polymorphism, the corporate

customer may respond to certain customer may respond to certain commands differently from another commands differently from another customercustomer

OperationsOperations

Most obviously correspond to the methods Most obviously correspond to the methods on a classon a class

UML syntax isUML syntax is visibility name (parameter list): return-type-expression {property string}visibility name (parameter list): return-type-expression {property string}

Class Diagrams:Class Diagrams:Advanced ConceptsAdvanced Concepts

Object DiagramObject Diagram

• A snapshot of the objects in a system at a point in time• Often called instance diagram• Let’s see the class diagram first

Partylocation

OrganizationPerson

* children

1 parent

Object Object DiagramDiagram

engineering:Organizationlocation=“boston”

tools:Organizationlocation=“Chicago”

apps:Organizationlocation=“Saba”

John:Personlocation=“Champaign”

Don:Personlocation=“Champaign”

parent

parent

This is associationsnot generalization orinheritance

this is objectnot class

Class Scope Operations and Class Scope Operations and AttributesAttributes

Order

getNumbergetNextNewNumber

instancescope

class scope

Class scope is equivalent to static members in C++

Multiple and Dynamic Multiple and Dynamic ClassificationClassification

Female

Male

PatientPhysio-therapist

Nurse

Doctor

FamilyDoctor

Surgeon

sex {complete}

role

patient

Discriminator

Multiple ClassificationMultiple Classification

DonDon’’t confuse with multiple inheritance.t confuse with multiple inheritance.You should make it clear which You should make it clear which

combinations are legal by using a combinations are legal by using a discriminatordiscriminator

Dynamic ClassificationDynamic Classification

Person

Male

Female

Salesman

Engineer

Manager

Job <<dynamic>>

sex{complete}

Dynamic ClassificationDynamic Classification

allow object to change type within the allow object to change type within the subtyping structuresubtyping structure

useful for conceptual modelinguseful for conceptual modelingHow to implement it? See Fowler 1997How to implement it? See Fowler 1997

Aggregation and CompositionAggregation and Composition

Aggregation is the part-of relationshipAggregation is the part-of relationshipdifficult things difficult things –– what is the difference what is the difference

between aggregation and association?between aggregation and association? It is vague and inconsistentIt is vague and inconsistent Anyway, UML decide to include aggregation Anyway, UML decide to include aggregation

and a stronger variety of aggregation called and a stronger variety of aggregation called compositioncomposition

Point

Style

colorisFilled

Polygon

Circleradius

{ordered}

3..*

*

1 1

*

1

Composition

aggregation

CompositionComposition

With composition, the part object may belong to With composition, the part object may belong to only one whole; further, the parts are usually only one whole; further, the parts are usually expected to live and die with the wholeexpected to live and die with the whole

deletion of the whole is considered to cascade to deletion of the whole is considered to cascade to the partthe part

In previous graph, deleting a polygon would In previous graph, deleting a polygon would caused its associated caused its associated Points Points to be deleted, but to be deleted, but not the associated not the associated StyleStyle..

Alternative Notation for Alternative Notation for CompositionComposition

Circle Polygon

Point

1

Point

{ordered} 3..*

Style

1 1

* *

Derived Associations and Derived Associations and AttributesAttributes

Derived Associations and derived Derived Associations and derived attributes can be calculated from other attributes can be calculated from other associations and attributes.associations and attributes. for example, an age attribute of a Person can for example, an age attribute of a Person can

be derived if you know that personbe derived if you know that person’’s birthday.s birthday.

Account/balance:Money

Entryamount:Money

SummaryAccount

DetailAccount

/entries *

{balance= sum of amounts of entries}

Components{hierarchy} *

0..1

Derivedattribute

Derived Association

1

NoteNote

Entry objects are attached to detail Entry objects are attached to detail AccountsAccounts

The balance of an Account is calculated The balance of an Account is calculated as the sum of Entry accountsas the sum of Entry accounts

A Summary AccountA Summary Account’’s entries are the s entries are the entries of its components determined entries of its components determined recursivelyrecursively

Interfaces and Abstract ClassesInterfaces and Abstract Classes

Programming language that use a single Programming language that use a single construct, the class, which contains both construct, the class, which contains both interfaceinterface and and implementationimplementation..

When you subclass, you inherit both.When you subclass, you inherit both.A pure interface, as in Java, is a class with A pure interface, as in Java, is a class with

no implementation and, therefore, has no implementation and, therefore, has operation declarations but no method operation declarations but no method bodies and no fields.bodies and no fields.

For exampleFor exampleinterface Stack { boolean Push(Object); Object Pop();}

Class MyStack implements Stack

boolean Push(Objects) { …….. }

Object Pop() { …….. return xxxx ; }}

Somewhere in initialization

Stack S = new MyStack() ;

Somewhere in the code

S.push(a);S.push(b);S.pop(a);S.pop(b);

text Editor

Window{abstract}

toFront()toBack()

Win98 Window

toFront()toBack()

X11 Window

toFront()toBack()

Mac Window

toFront()toBack()

Dependency

InputStream

DataInputStream

<<interface>>DataInput

OrderReader

Realization

generalization

dependency

Abstract Class and InterfaceAbstract Class and Interface

two are similartwo are similarabstract class allows you to add abstract class allows you to add

implementation of some of the methodsimplementation of some of the methodsan interface forces you to defer definition an interface forces you to defer definition

of all methodsof all methods

Classification and Classification and GeneralizationGeneralization

People often talk subtyping as the People often talk subtyping as the ““is ais a”” relationship relationship beware of that way of thinkingbeware of that way of thinking for examplefor example

1. Shep is a border Collie1. Shep is a border Collie2. A border Collie is a Dog2. A border Collie is a Dog3. Dogs are animals3. Dogs are animals4. A border Collie is a Breed (4. A border Collie is a Breed ( 品種品種 ))5. Dog is a Species (5. Dog is a Species ( 物種）物種）

if you try combination 2 and 5 if you try combination 2 and 5 ““A border Collie is a SpeciesA border Collie is a Species””. This . This is not goodis not good

The reasons?The reasons? some are classification and some are generalizationsome are classification and some are generalization

Generalization is transitive and classification is notGeneralization is transitive and classification is not ““Dog are a kind of animalsDog are a kind of animals”” is better is better

Qualified AssociationsQualified Associations

equivalent to associative arrays, maps, and dictionariesequivalent to associative arrays, maps, and dictionaries an example, there maybe one Order Line for each an example, there maybe one Order Line for each

instance of Productinstance of Product Conceptually, you cannot have two Order Lines within an Conceptually, you cannot have two Order Lines within an

Order for the same productOrder for the same product

Order

Order Line

amount:Numberproduct

0..1

line item

Qualified association would imply an interface like

class Order {

public OrderLine getLineItem (Product aProduct);;

public void addLineItem (Number amount, Product forProduct);}

Order

Order Line

amount:Numberproductline item

You can have multiple OrderLines per Product but You can have multiple OrderLines per Product but access to the Line Items is still indexed by Productaccess to the Line Items is still indexed by Product

use an associative array or similar data structure to hold use an associative array or similar data structure to hold the order linesthe order lines

Class Order {Class Order { private Map _lineItems ;private Map _lineItems ;

*

Association ClassAssociation Class

Association class allow you to add attributes, Association class allow you to add attributes, operations, and other features to associationoperations, and other features to association

Person Company

Employment

period:dateRange

employer*

association class

0..1

A person may work for a single companyA person may work for a single company We need to keep information about the period We need to keep information about the period

of time that each employee works for each of time that each employee works for each CompanyCompany

You can redraw: make Employment a full You can redraw: make Employment a full class in its own rightclass in its own right

Employment

period:dateRange

Person Company1 0..1 * 1

/employer0..1*

Parameterized ClassParameterized Class

Several language, noticeably C++, have the Several language, noticeably C++, have the notion of a parameterized class or templatenotion of a parameterized class or template

exexclass set <T> {class set <T> { void insert (T newElement); void insert (T newElement); void remove(T anElement); void remove(T anElement);…………Set <Employee> employSet ;Set <Employee> employSet ;

A define a parameterized class A define a parameterized class in UMLin UML

Set

insert(T)remove(T)

T

templateParameter

templateclass

A use of a parameterized classA use of a parameterized class

Set

insert(T)remove(T)

T

EmployeeSet<Employee>

<<bind>>

Bound Element

VisibilityVisibility C++C++

A public member is visible anywhere in the program and may be A public member is visible anywhere in the program and may be called by any object within the systemcalled by any object within the system

A private member may be used only by the class that defines itA private member may be used only by the class that defines it A protected member may be used only by (a) the class that A protected member may be used only by (a) the class that

defines it or (b) a subclass of that classdefines it or (b) a subclass of that class

In JavaIn Java a protected member may be accessed by subclasses but also a protected member may be accessed by subclasses but also

by any other class in the same package as the owning classby any other class in the same package as the owning class C++C++

one C++ method or class can be made a friend of a class. A one C++ method or class can be made a friend of a class. A friend has complete access to all members of a classfriend has complete access to all members of a class