1 UML Class Diagram Class Association and a little about Object Diagrams

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UML Class Diagram

Class

Association

and a little about Object Diagrams

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The reality and UML-models

Business processes(in Activity Diagram)

Communication between people(in Sequence Diagram

Sequens DiagramActivity Diagram

Use case

The reality UML-models

Business concepts(in Class Diagram)

Information Model (in Class Diagram)

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Class Diagrams – central in UML

The Class Diagrams are the majority – have almost become synonymous with UML.

Class Diagrams describes Classes in a domain or in a system, and static associations between the classes.

Class Diagrams also shows the attributes and operations of the classes.

Studentpersonalnrnameemail

registerForCourse()

CoursecourseIDcourseName

Note that following words have been used as synonymes:

• type och class,• relation och association,• structural och static.

In UML-context we should use the concepts marked in bold letters.

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Classes – UML-notation

The UML-notation for a class is a rectangle with (normally) three sections or compartments.• the compartment at the top contains the name of the class in bold letters and a capital first letter.• the compartment in the middle contains the names of the attributes in the class.• the compartment at the bottom contains the names of the operations in the class.

Note the way to write the names of the attributes and operations – yet a convention and no formal rules:

- begins with a small letter, a capital letter can be placed in the middle if it consists of several words.

- name of the class and –names of the attributes are written as substantives or substantive phrases, names of classes begin with a capital letter.

- operations are written as verbs, also note the parentheses after the operation name.


registerForCourse()

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Classes – variants of notations

Class name

AttributesOperations


registerForCourse()requestIncreasedAccount()


Student

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Classes – objects, attributes & methods

Attributes:are used to describe static characteristics within a class. Are given values in their objects.

Operations:are spoken about at class level when to represent the dynamic behaviors of the objects. Operations are called methods at the object level.

Objects:

Students can have a lot of similarities, for example e-mail, and they can register for courses.

We collect similarities and create the class Student. Every student is now an object of the class Student.

All Student objects have a value on the attributes and are able to perform the methods.


registerForCourse()requestIncreasedAccount()

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Class Diagram and Object Diagram

Studentpersonalnrnameaddressemail

annaSvan:Studentpersonalnr = ”770102-XXXX”name = ”Anna Cecilia Svan”address = ”Ekvägen 10”email = ”[email protected]”

nilsHall:Studentpersonalnr = ”850302-XXXX”name = ”Nils Erik Hall”address = ”Rågstigen 3”email = ”[email protected]”

Object DiagramClass Diagram

Often called Instance Diagram.

Increased notation för naming.

Attributes gets values.

All associationes from the Clas Diagram follows to the objects.

Can be seen as a snapshot of one or more objects at a certain moment. Why? The values of the attributes can be changed during the lifecycle of the objects.

Class Object (instance)Object (instance)

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Attributes & associations are properties


Course

courseIDcourseName

RegistrationregistrationIDdate

Properties (characteristics)

- is UML’s umbrella term for the attributes and associations of classes.

- models the static (structural) characteristics of classes.

Associations

Attributes

Properties

Properties

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Properties have multiplicity

The multiplicity for a property (attribute or association) indicates how many different objects (or values) that are able to fulfil the property.

Multiplicity for associations is stated at each assoiciated class.

The complete way to write multiplicity , is that:

- the smallest number is stated first,

- the largest number is stated last,

- two dots are written between the numbers.


Course

courseIDcourseName


0..*1..1 0..* 1..1[1..1][1..1][1..*]

[1..1][1..1]

[1..1][0..1]

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Multiplicity – usual combinations

1..1 Minimum 1 and maximum 1. Example: A student has one, and only one, value at the attribute personalnr.

1..* Minimum 1 and an infinite upper number. Example: A student is always given one e-mail address, but can have many more e-mails.

0..* 0 is valid and an infinite upper number. Example: A student does not have to be registered on a course, but can be registered on many courses.

0..1 0 is valid and maximum 1. Example: A course does not need to have been given a name and can possibly have one name.


Course

courseIDcourseName


0..*1..1 0..* 1..1[1..1][1..1][1..*]

[1..1][1..1]

[1..1][0..1]

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Multiplicity for associations

multiplicity describes how many different objects that can be part of an association between two classes.

Exemple:

A Student object is associated to zero-to-many Registrations.

A Registration object is associated to one-to-one, i.e. exactly one, Student.


Course

courseIDcourseName


0..*1..1 0..* 1..1

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More about multiplicity for associations

Student CourseRegistration0..*1..1 0..* 1..1

anna:Student

nils:Student

9:Registration

2:Registration

oop:Course

oos:Course

jök:Coursetove:Student6:Registration

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Multiplicity of associations with Venn-diagram

Anna

Nils

Tove

Registration

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2

9

Student Course

oop

oos

jök

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Notes

Notes is comments in UML-diagrams.

Not connected to any special modelling element

If notes is about a special modelling element it is connected to the element with a broken line. Note that the line ends with a small unfilled circle.

Notes can also be used to state constraints for the modelling element. The constraints then have to be written within curly braces. Constraints can also be written in text or more formally.

StudentIncludes University students, but not secondary school students.

{ Only students living at IP }

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Attribute - notation

visibility name type multiplicity = default value {property}

Anställd+ companynr: Integer [1..1] = 4222 {readOnly}

There are publik (+), privat (-), protected (#) visibility, and packet visibility (~).

The only mandatory part in the notation of the attribute.

The data type of the value. Limits which type of values the attributes can have.

Multiplicity

Automaticly assignedwhen an object is created.

Perhaps furtherproperties of the attribute.

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Operationes - notation

visibility name (parameter list) : return type {property}

Employee

+ getNamn (employeenr:Integer): String

+ companynr: Integer [1..1] = 4222 {readOnly}

There are publik (+), privat (-), protected (#) visibility, and packet visibility (~).

The only mandatory part in the notation of the operation.

List of the parameters used by the operation. It can be input (in), output (out), or both (inout).

The data type of the returnedvalue.

Perhaps furtherproperties of the operation.

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UML-concept feature

Attribute OperationsAssociations

properties

Features

DynamicStaticfeatures features

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To name associations

Three ways to name associations:1) with a verb at each class.

Student Teacher0..*

1..* employeenr [1..1]]studregnr [1..1] is supervising

is supervised

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Three ways to name associations:2) Only one verb at the association line

.

Student Teacher0..*

1..1 employeenr [1..1]studregnr [1..1] supervise

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Three ways to name associations: 3) With a substantive at each class.

Student Teacher0..*

1..* employeenr [1..1]studregnr [1..1] thesiswriter

supervisor

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Class Diagram – a summary

Classes

Attributes

Operations

Associations

annaSvan: Studentpersonalnr = ”770102-XXXX”name = ”Anna Cecilia Svan”email = ”[email protected]”

Multiplicity

registerForCourse()

Objects

Notes


Registration

0..*1..1

[1..1][1..1][1..*]

[1..1][1..1]

registrationIDdate

registerForCourse() listRegistrations()

Includes University students, but not secondary school students.

.

Documents

1 UML Class Diagram Class Association and a little about Object Diagrams