Wk4 UML AdvClassDiagrams[1]

8/2/2019 Wk4 UML AdvClassDiagrams[1]

1/45

www.ddss.arch.tue.nl

7M822

UML Class Diagrams

advanced concepts

15 September 2008


2/45


7M822

UML Class Diagrams

The class diagram provides a static structure of all theclasses that exist within the system. Classes are arrangedin hierarchies sharing common structure and behaviourand are associated with other classes.

Class diagrams are used in:

Analysis To build a conceptual domain model with semanticassociations between concepts

Design Structural model of a design in terms of class interfaces Implementation Source code documentation, exposing the

implementation


3/45


7M822

An object is a thing that can be tangible orintangible.Examples tangible: bike, car, house

intangible: order, account

Objects

An object has properties.Example

a Customerhas aname and address

Customer

NameAddress


4/45


7M822

Property of object = attribute+ value

(Multiple) Objects

Adacs: Customer

Name = AdacsAddress = Enschede

Primo: Customer

Name = PrimoAddress = Grave

Multiple objects unique identity1247: Customer

Custno = 1247Name = AdacsAddress = Enschede

9378: Customer

Custno = 9378Name = PrimoAddress = Grave


5/45


7M822

Link = connection between objects

Connection between Objects

1247: Customer

Custno = 1247

Name = AdacsAddress = Enschede

345T7: Order

Orderno = 345T7

dateReceived = 10/10/05Price = 1987

902U2: Order

Orderno = 902U2dateReceived = 07/04/05Price = 3789


6/45


7M822

Class class is abstract concept each object is instance of a class classes classify objects

attribute has no values

Class

Customer

CustnoNameAddress

Order

OrdernodateReceivedPrice

Object analysis than values to attributes


7/45


7M822

Attribute has no valuesAssociation is relation between classes

Class Diagram

Customer

CustnoNameAddress

Order

OrdernodateReceivedPrice

Link is instance of association

1 *


8/45


7M822

Class diagram

A class diagram describes the type of objects in a systemand the static relationships between them.

Static relations:

Associations

Subtypes

Static structure:

Attributes

Operations


9/45


7M822

Class operations

An operation is the implementation of a service that can be requestedfrom any object of the class in order to affect behaviour.

Operations are used to manipulate the attributes or to perform other

actions. Operations are normally called functions, but they are inside aclass and can be applied only to objects of that class.

An operation is described with a return-type, a name and zero or moreparameters. Together, the return-type, name, and parameters arecalled the signature of the operation.

The signature describes everything needed to use the operation.


10/45


7M822


11/45


7M822

Class - associations

Associations are structural relationships where instances (objects) ofone class are connected to instances (objects) of another class.

an employee works for a company

a company has a number of offices An association is normally bidirectional, which means that if an object

is associated with another object, both objects are aware of each other(navigation is bidirectional by default).

Binary association connects exactly two classes. N-ary connects many

classes. The most common association is just a connection between classes.


12/45


7M822

Association adornments: name, role

The association has a name - the descriptive term, often a verb, forthe association.

Each association has two association ends; each end is attached to

one of the classes in the association. An end can be explicitly namedwith a label. This label is called a role name (association ends areoften called roles).

Person Company

employee employer

works for

Person Company

employee employer

has employment for


13/45


7M822

Associations: multiplicity

Multiplicity defines the number ofobjects associated with aninstance of the association.

Default of 1 (1: 1) 0 or 1: 0..1

Zero or more (0..infinite): *

1 or more (1..infinite): 1..*

n..m; range from n to m inclusive

Car Person

transports

passenger

Car Person

transports

passenger

5

Car Persontransports

passenger

*

Car Person

transports

passenger

1..*

Car Person

transports

passenger

2..5


14/45


7M822

dd h l


15/45


7M822

Generalization

A specialization / generalizationrelationship, in which objects ofthe specialized element (child)

are substitutable for objects ofthe generalized element(parent). Superclass the generalization of

another class, the child.

Subclass the specialization of

another class, the parent.

Customer

Corporate

Customer

Personal

Customer

dd h l


16/45


7M822

Generalization - characteristics

Identify common features concerning behaviour andknowledge. Define these common features on a higherlevel in the inheritance hierarchy.

The aim is at behaviour more than knowledge whencombining classes.

Generalization is a bottom-up process.

A superclass includes all common properties of itssubclasses.

dd h t l


17/45


7M822

Specialization - characteristics

Define a new class which is a special appearance of anexisting class.

Specialization is a top-down process.

A subclass can have attributes and operations that arespecific for that sub-class.

A subclass may redefine operations of its super-class

dd h t l


18/45


7M822

dd h t l


19/45


7M822

Constraints

The basic constructs of association, attribute, andgeneralization do much to specify important constraints.

They cannot indicate every constraint. These constraintsstill need to be captured; the class diagram is a goodplace to do that.

The UML allows you to use anything to describeconstraints. The only rule is that you put them inside

braces { }.

dd h t l


20/45


7M822

www ddss arch tue nl


21/45


7M822

Attribute analysis

It is not always clear which attributes belongs to which classes byfinding out the class attributes. An attribute is assigned to that classwhere it is certainly a feature.

For example: a project leader has the attributes name, departmentand age.

But what to do with the attributes project number, project duration,starting time, and budget? These attributes clarifies something aboutthe relation between project leader and type of project.

This often happens if a n:m relation refers to an association betweentwo classes. In that case, we can define a new class, for instanceproject management.


22/45



23/45


7M822

Aggregation and Composition: example

Chess set

Board

+kleur() : {w,b}

-column : A..H

-row : 1..8

Field

-color : {w,b}

Piece

1

1

1

*

1 *64 1 0..1

Pawn Bishop Knight Rook Queen King



24/45


7M822

Object diagram

An object diagram is a diagram that shows a set ofobjects and their relationships at a point in time; objectdiagrams address the static design view or static process

view of a system.

An object diagram is shown as a class, and the name isunderscored, although an objects name can be shown

optionally preceding the class name as: objectname:

classname. The object does not have to be named, inwhich case only the classname is shown underscored.



25/45


7M822

Object diagram: example



26/45


7M822

Advanced Class Features



27/45


7M822

Advanced Class Concepts : Visibility

Visibility class members (attributes, operations) may bespecified as:{we have feature f, an attribute or operation that is defined on an object O ofclass C }

+ :public{f is publicf is visible to any object and f is inherited by the subclasses of C.}

# : protected{f is privatef is visible only to O and f is not inherited by the subclasses of C.}

- : private

(f is protectedf is visible only to objects of class Cand to objects of Cssubclasses and f is inherited by the subclasses of C.}

Restricting visibility is the same as restricting accessibility.



28/45


7M822

Advanced Class Concepts : Scope

Individual member data (= attributes) may have:

Class scope : a single copy of an attribute is shared by allinstances of a class.

Instance scope : each instance of a class would have its own copyof the attribute.


29/45



30/45


7M822

Advanced Class Concepts : Abstract

An operation is abstract if it has no implementation.

A abstract class cannot have any direct instances.

Abstract classes only occur in the context of aninheritance hierarchy.

Abstract operations and classes are specified by

writing its name in italics.



31/45


7M822

Advanced Class Concepts : Abstract cont.



32/45


7M822

Interfaces and Abstract Classes

One can vary the interfaces of classes independent ofthe implementation.

A pure interface is a class with no implementationand, therefore has operation declarations but nomethod bodies an fields.

Interfaces are often declared through abstract

classes.



33/45


7M822

Window as Abstract Class



34/45


7M822

Interfaces and Abstract Class

Sub classing is not only the way to do this.

For instance Java provides an interface construct, and the compilerchecks that the implementing class provides implementations of all the

interfaces operations.



35/45


7M822

Lollipop notation for Interfaces



36/45


7M822

Aggregation and Composition once more

Aggregation is a special form of association that specifies awhole-part relationship between the aggregate (the whole) anda component (the part); aggregation is the part-of relationship.{it is a special form of association in which a collection of objects, each havingan independent existence, is associated with an single object} {unfilleddiamond}

Composition is a form of aggregation with strong ownershipand coincident lifetime of the parts by the whole; the part objectmay belong to only one whole the parts are usually expectedto live and die with the whole.

{usually, any deletion of the whole is considered to cascade to the parts}{filleddiamond}



37/45

ddss a c tue

7M822

Aggregation and Composition once more, cont.

Computer system

Monitor

Building

Floor

Computer system

Monitor

Building

Floor

1

1

1

1..*

1

1..2

1

*



38/45

7M822

Aggregation and Composition: Example



39/45

7M822

Alternative notation for Composition



40/45

7M822

Derived Associations and Attributes

Derived associations andattributes can be calculated froother associations andattributes, respectively, on aclass diagram.

For example, an age attributeof a Person can be derived ifyou know that Persons date of

birth.



41/45

7M822

Derived Associations and Attributes example



42/45

7M822

Qualified Associations

The qualifier specifies how a specific object at the manyend of the association is identified, and may be seen as akind of key separating all the objects in the association.



43/45

7M822

Relations and Constraints



44/45

7M822

Reflexive Associations

A class has an association to itself.

Example: A directory may contain other directories.

Directory File

0..1parent

subdirectory

0..*

1 0..*



45/45

References

Sommerville, Ian (2001)

Software Engineering, 6thedition

http://www.software-engin.com

Grady Booch, James Rumbaugh, Ivar Jacobson (2005)

The Unified Modeling Language User Guide, 2ndedition

Martin Fowler (2000, 2004)

Object-Oriented Software Engineering, 2ndedition; 3rdedition
http://www.software-engin.com/http://www.software-engin.com/http://www.software-engin.com/http://www.software-engin.com/

Wk4 UML AdvClassDiagrams[1]

Documents

Transcript of Wk4 UML AdvClassDiagrams[1]