advanced uml class diagrams

1© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

Advanced UML Class Advanced UML Class DiagramsDiagrams


ObjectivesObjectives

To present the portions of the UML class diagram notation not already covered

To present examples to illustrate the use of the notation

To present heuristics for using the notation well


TopicsTopics

Generalization Abstract and concrete operations and classes Interfaces Feature visibility Class and instance variables and operations Aggregation and composition Association classes and qualifiers Other association adornments More class diagram heuristics


GeneralizationGeneralization

Generalization is the UML relation that holds between one model element (the parent) and another (the child) when the child is a special type of the parent.

• Represented by a hollow rectangle and lines

• Rectangle attaches to the parent and lines to the children

Generalization is used in UML class diagrams to model inheritance.


Generalization ExampleGeneralization Example

Mammal

PumaTiger

Feline

Quadruped

Lion

Lizard


Generalization versus Generalization versus AssociationAssociation

Generalization is a relation between classes.

Associations represent relations on sets of class instances designated by the associated classes.

Generalization is not a kind of association. They

• Never have multiplicities,• Never have rolenames,• Never have names (they already have a

name: generalization).


Abstract Operations and Abstract Operations and ClassesClasses

An abstract operation is an operation without a body; a concrete operation has a body.

An abstract class is a class that cannot be instantiated; a concrete class can be instantiated.

A class • Must be abstract if it has an abstract

operation;• May be abstract even if it has no abstract

operations.


Using and Representing Using and Representing Abstract Classes and Abstract Classes and OperationsOperations

Abstract classes force their subclasses to implement certain operations.

Abstract classes are represented in UML by

• Italicizing their names,• Stereotyping them «abstract» or• Giving them an {abstract} property.

Abstract operations are represented in UML by

• Italicizing their specification or• Giving them an {abstract} property.


Abstract Class and Abstract Class and Operation ExamplesOperation Examples

Circle ScreenRenderer Book

Document{ abstract }

callNumberdescriptors : String[*]render()

Renderer«abstract»

Shape

areaOf() : float { abstract }


InterfacesInterfaces

A UML interface is named collection of public attributes and abstract operations.

• Provided interfaces—realized by a class or component and represented by A ball (lollipop) symbol or A stereotyped class icon with a realization

connector

• Required interfaces—needed by a class or component and represented by A socket symbol or A dependency arrow to a ball symbol or A dependency arrow to a stereotyped class icon


Provided Interface Provided Interface NotationsNotations

TimerObserver

Observer

TimerObserver

«interface»Observer

update( arg : Object )


Required Interface Required Interface NotationsNotations

Observer

TimerObserver



TimerTimer

Observer

Timer


Module Assembly Module Assembly NotationsNotations



Timer

Observer

Timer

TimerObserverTimerObserver


UML Feature VisibilityUML Feature Visibility

Public—Visible anywhere that the class in which it appears is visible; denoted by +.

Package—Visible anywhere in the package containing the class in which it appears; denoted by ~.

Protected—Visible in the class in which it appears and all its sub-classes; denoted by #.

Private—Visible only in the class in which it appears; denoted by -.


Feature Visibility Feature Visibility ExampleExample

Alarm

+ identifier : String {constant}# location : String# description : String- classification : Classifier

+ getLocation() : String+ getDescription() : String+ action()~ setClassification( c : Classifier)~ getClassification() : Classifier# basicAction()

FireAlarm IntrusionAlarm FloodAlarm


Class and Instance Class and Instance Variables and Variables and OperationsOperations

An instance variable is an attribute whose value is stored by each instance of a class.

A class variable is an attribute whose value is stored only once and shared by all instances.

An instance operation must be called through an instance.

A class operation may be called through the class.

In UML class variables and operations are called static.

• Indicated by underlining an attribute’s or operation’s specification


Attribute and Operation Attribute and Operation Specification ExamplesSpecification Examples

Tokenizer

+ token : TokenType = NONE+ tokenText : String- buffer : String- bufferPosition : integer- delimiters : String

- theInstance : Tokenizer

+ getInstance() : Tokenizer+ nextToken()+ setBuffer( buffer : String )+ setDelimiter( delim : String )

TokenType

+ NONE : TokenType { constant }+ NUMBER : TokenType { constant }+ IDENTIFIER : TokenType { constant }+ EQUAL : TokenType { constant }+ MINUS : TokenType { constant }+ PLUS : TokenType { constant }- name : String

- TokenType( name : String )+ toString() : String


Aggregation and Aggregation and CompositionComposition

The aggregation association represents the part-whole relation between classes.

• Denoted by a solid diamond and lines• Diamond attaches to the aggregate (whole)

while lines attach to the parts• May have all association adornments

The composition association is an aggregation association in which each part can be related to only one whole at a time.

• Denoted by a hollow diamond and lines


Aggregation and Aggregation and Composition ExamplesComposition Examples

Human

FamilyChurch

Person

FootHand

LegArm

0..2 0..2

0..1 0..1

*

1..*

1..*

1..*


Problems with Problems with AggregationAggregation

Often abused• Must be transitive:

(x)(y)(z)((Rxy • Ryz) Rxz)

• Often used for collection membership, which is not transitive

Aggregation, composition, and collection membership can be represented by plain associations.


Association ClassesAssociation Classes

An association class represents a relation on instances of the classes is connects, and it holds data and behavior.

• Association class connector is a dashed line• Connects class with an association line

There can be only one instance of an association class for each pair of instances of the associated classes.

If more instances are need, interpose a new class (a reified association).


Association Class Association Class ExampleExample

Medication Patient* *

Prescription

- date


Association QualifiersAssociation Qualifiers

An association qualifier is one or more association attributes that, together with instances of the qualified class, pick out instances of an associated target class.

• Represented by a box with association attributes and a line

• Attributes have standard specifications except that no initial values are allowed

• Box is attached to the qualified class• Line runs to the target class• Line can have association adornments


Association Qualifier Association Qualifier ExamplesExamples

Catalog

Course

departmentnumber

List

Object

index:int

0..1 0..1

1..**


Rolename VisibilityRolename Visibility

Associations are often implemented using references.

• Rolename may be a reference attribute name

Rolenames may have visibility modifiers (+, #, ~, -).

Rolename visibility modifiers may be suppressed.


Association NavigabilityAssociation Navigability

An association between classes A and B is navigable from A to B if an instance of A can access an instance of B; otherwise it is non-navigable.

• Navigability is denoted by adding an arrowhead to the association line in the navigation direction

• Non-navigability is denoted by placing an x on the association line in the navigation direction

• Navigability markers can be suppressed, so no markers means the diagram is silent on navigability


Rolename Visibility and Rolename Visibility and Navigability ExampleNavigability Example

Game

Player

Referee

- player1..*

*

0..1 - myGame

1


Class Diagram Class Diagram Heuristics 1Heuristics 1

Never place a name, rolenames, or multiplicities on a generalization connector.

Use the «abstract» stereotype and {abstract} property to indicate abstract classes and operations when drawing diagrams by hand; use italics when drawing diagrams on the computer.

Use the interface ball and socket symbols to abstract interface details and a stereotyped class symbol to show details.



Don’t italicize interface or operation names.

Show provided interfaces with the interface ball symbol or the stereotyped class symbol and a realization connector.

Show required interfaces with the interface socket symbol or dependency arrows to stereotyped class symbols or interface ball symbols.

Avoid aggregation and composition.



If aggregation or composition is used, check that the represented relation is transitive.

Use association classes when only a single association class instance is associated with each pair of instances of the associated classes; otherwise use a reified association.

Determine multiplicities involving a qualifier by considering qualified class instances and particular combinations of qualifier attribute values.


SummarySummary

UML class diagrams have great expressive power: they are able to show

• Generalization• Abstract operations and classes• Class and instance variables and operations• Interfaces and interface assemblies• Aggregation and composition associations• Association classes and quantifiers• Feature and rolename visibility• Navigability

advanced uml class diagrams

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