[Fundamental] UML Class Diagrams

Overview

A UML class diagram describes the object and information structures used by your application, both internally and in communication with its users.

example

Taken from here.

Shape

Element

Description

1

Class

A definition of objects that share given structural or behavioral characteristics. For more information, see Properties of types on UML class diagrams.

1

Classifier

The general name for a class, interface, or enumeration. Components, use cases, and actors are also classifiers.

2

Collapse/ Expand control

If you cannot see the details of a classifier, click the expander at upper-left of the classifier. You might also have to click the [+] on each segment.

3

Attribute

A typed value attached to each instance of a classifier.

To add an attribute, click the Attributes section and then press ENTER. Type the signature of the attribute. For more information, see Properties of attributes on UML class diagrams.

4

Operation

A method or function that can be performed by instances of a classifier. To add an operation, click the Operations section and then press ENTER. Type the signature of the operation. For more information, see Properties of operations on UML class diagrams.

5

Association

A relationship between the members of two classifiers. For more information, see Properties of associations on UML class diagrams.

5a

Aggregation

An association representing a shared ownership relationship. The Aggregation property of the owner role is set to Shared.

5b

Composition

An Association representing a whole-part relationship. The Aggregation property of the owner role is set to Composite.

6

Association Name

The name of an association. The name can be left empty.

7

Role Name

The name of a role, that is, one end of an association. Can be used to refer to the associated object. In the previous illustration, for any Order O, O.ChosenMenu is its associated Menu.

Each role has its own properties, listed under the properties of the association.

8

Multiplicity

Indicates how many of the objects at this end can be linked to each object at the other. In the example, each Order must be linked to exactly one Menu.

* means that there is no upper limit to the number of links that can be made.

9

Generalization

The specific classifier inherits part of its definition from the general classifier. The general classifier is at the arrow end of the connector. Attributes, associations, and operations are inherited by the specific classifier.

Use the Inheritance tool to create a generalization between two classifiers.