Four types of relationships in UML and four types of UML

Four types of relationships in UML and four types of UML

1. Association

Description: Assocition: Describes the structural relationship between two or more classes.

(1) Common Association:

1) Association name: used to describe the nature of the link.

2) Role: When a class is at one end of the Association, the class plays a specific Role in the relationship; A role is the responsibility of a class close to one end of the Association to present classes at the other end.

3) Multiplicity multiple: the multiple associated roles indicate the number of connected objects in an associated instance.

For example ():

 

Public Class Person

    Private employer As Company

End Class

 

Public Class Company

    Private employee As Person

    '……

End Class

 

 

For example:

Public Class CatalogEntry

    Private name As String

    Private number As Integer

    Private cost As Double

    Public Function getCost() As Double

        Return cost

    End Function

End Class

Public Class Part

    Private entry As CatalogEntry

    Public Function Cost() As Double

        Return entry.getCost

    End Function

End Class

 

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        Dim screw As New CatalogEntry("screw", 28834, 0.02)

        Dim screw1 As New Part(screw)

        screw1.Cost()

        '……

    End Sub

 

In the two examples above, the first is a two-way normal Association, and the second is a one-way Association. Likewise, two classes can have multiple associations, one class can be associated with multiple classes, and the other class can be associated with itself.

(2) aggregate aggregation

Note: Aggregation indicates A weak "ownership" relationship, which indicates that object A can contain object B, but object B is not part of object.

Example:

Public Class GooseGroup

    Private arrayWildGoose As New WildGoose()

    '……

End Class

 

(3) composition

Note: A strong "ownership" relationship represents a strict part and the overall life cycle is the same.

For example:

Public Class Bird

Private wing As Wing

Public Sub New ()

Wing = New Wing () 'in the bird class, the Wing wing Wing is instantiated during initialization, and both of them are generated at the same time.

End Sub

End Class

 

Ii. Generalization generalized relationship

Note: It is a special/general relationship. Objects of special elements (child elements) can replace objects of general elements (parent elements. In this way, the child element shares the structure and behavior of the parent element.

Representation Method:

Public Class Dog : Inherits Animal

'……

End Class

 

NOTE: If VB.net indicates that a class is no longer inherited, you can use notInheritable.

Iii. Dependency

Dependency:

For example:

Note: animals have several major features, such as metabolism and reproduction. Animals must have vitality and need oxygen, water and food. That is to say, animals depend on oxygen and water. Dependency between them, expressed by the dotted arrow

For example:

Public Class Professor

    Public Function Teach(ByVal c As Course)

        '……

    End Function

End Class

 

NOTE: If two classes have a structural relationship (association relationship), there is no dependency relationship (two things generally have this relationship)

 

IV. Implementation of Realization

Note: Implementation refers to the semantic relationship between class elements. In this relationship, one class element describes the contract implemented by another class Element guarantee.

Representation Method:

Public Interface IShape

    Function Draw()

End Interface

 

Public Class Circle : Implements IShape

    Public Function Draw() Implements IShape.Draw

    End Function

End Class