Multiplicity in UML: Airplane Example

Wings

Hull

• An Airplane has 0 or more Engines.

  • Gliders have none
  • Commercial aircraft have several

• An aircraft Engine, if it exists, must belong to an Airplane.

• A Landplane has 2 or more Wheels.

• A Wheel optionally belongs to a single Landplane.

Airplane

Seaplane

Landplane

Wheel

2..*

0..1

* means 0 or more,

sometimes called many.

N..* means N or more.

Engine

*

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