UML Reference

The Unified Modeling Language (UML) is a language which can be used to model software systems. It is is not a programming language or a tool. With UML you can specify (what and how), visualize, construct, and document artifacts (= deliverables, such as documents, source code etc).

UML was conceived by Rational Software Corporation and three persons Grady Booch, James Rumbaugh, and Ivar Jacobson.

UML is maintained by the Object management Group (OMG) and more information can be found at their website:

This UML reference contains brief summaries of UML elements. All drawings are created with ArgoUML.


The number of objects involved is indicated by the multiplicity. If this is omitted than by default 1 is assumed.

See association for an example.

The following (example) multiplicity values can be given:

1Default if omitted
*zero or more
1..*1 or more
0..1zero or 1
2..5At least 2 and up to 5
2,52 or 5
nUnknown at compile time