UML Class and Object Icons

A UML class represents a class. This could be a class of analysis objects, a design-time class, or an implementation class (Java, C++, C#, etc.)

A UML class icon has three compartments:

Stereotypes

The top compartment contains the name of the class and its optional stereotype.

A stereotype can be used to show an informal role or category of a class.

In an analysis model typical stereotypes are:

<<entity>> = a domain-specific object such as a bank account or employee

<<control>> = an object that excutes user commands

<<boundary>> = an interface between an actor and a control. A control panel, for example.

<<actor>> = a person, device, or server that interacts with a system

Entity classes can be further subdivided into:

<<thing>> = an entity that has mass and volume

<<event>> = an entity that has a start time and duration

<<role>> = an entity that executes tasks. For example: plumber, clerk, nurse

<<type>> = an entity that describes other entities: film genre (Sci Fi, comedy, etc.), film rating (P, PG, etc.)

A well known design-time stereotype:

<<interface>> = a collection of related operations that must be implemented

The middle compartment contains the attributes all instances of a class will have.

An attribute has four properties:

name

type (this can be a primitive type such as int, boolean, or double or an external class such as String or Money)

visibility (+ = public = system visibility, ~ = package visibility, # = protected = sub-class visibility, - = private = class visibility)

initial value

The third compartment contains the operations that instances of the class can execute.

Note that an operation is a method without an implementation:

method = operation + implementation

An operation has four properties:

name

scope (same as above)

parameters (each parameter has a name and type)

return type (usually supressed if void)

An object icon has the form:

Note that the attribute-value compartment and name are optional.

For example:

Note that the operations are not shown. This would be tiresome since the operations are the same for all instances of a class.

A package icon is a folder:

For example, most of the Java class library is contained in the java package:

This package contains sub-packages such as:

In addition to libraries, packages often contain models:

And sub-systems:

A note is the UML equivalent of a comment: