The Unified Modeling Language(UML) is a general-purpose, developmental, modeling language in the field of software engineering that is intended to provide a standard way to visualize the design of a system.

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主要说说UML中的关系(Class Relationships)

reference1, reference2

Class Relationships

A class may be involved in one or more relationships with other classes.

Inheritance(or Generalization)

Represents an “is-a” relationship
An abstract class name is shown in italics
SubClass1 and SubClass2 are specializations of Super Class
A solid line with a hollow arrowhead that point from the child to the parent class

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classDiagram
Class <|-- SubClass1
Class <|-- SubClass2

Simple Association

A structural link between two peer classes
There is an association between Class1 and Class2
A solid line connecting two classes

1 2	classDiagram Class1 .. Class2

Aggregation

A special type of association. It represents a “part of” relationship.

Class2 is part of Class1.
Many instances(denoted by the *) of Class2 can be associated with Class1
Objects of Class1 and Class2 have separate lifetimes
A solid line with an unfilled diamond at the association end connected to the class of composite

1 2	classDiagram Class1 o-- Class2

Composition

A special type of aggregation where parts are destroyed when the whole is destroyed.

Objects of Class2 live and die with Class1
Class2 cannot stand by itself
A solid line with a filled diamond at the association connected to the class of composite

1 2	classDiagram Class1 *-- Class2

Dependency

Exists between two classes if the changes to the definition of one may cause changes to the other (but not the other way around)
Class1 depends on Class2
A dashed line with an open arrow

1 2	classDiagram Class1 ..> Class2