UML Arrows Explained - Know UML Relationship Types
UML diagrams use different types of arrows. Each arrow type represents another relationship. Sometimes the relationships are depicted in the same way, but they have a slightly different meaning. In that case, they can be annotated with a stereotype.
UML Class Diagram Arrows and Relationships
Different arrows have different meanings in class diagrams. They represent various types of relationships.
UML class diagram arrows
Class diagrams use these UML arrows and connectors:
- A solid line without any decoration represents an association.
- Triangle connectors:
- A triangle-head arrow with a solid line represents a generalization.
- A triangle-head arrow with a dashed line represents a realization.
- Arrow connectors:
- An arrow with a dashed line is used for dependencies. Except for a general dependency it may be further specialized as
- An arrow with a solid line represents a directional association.
- A double-arrowed line is used for bidirectional association.
- Diamond connectors:
- A filled diamond (or black diamond) with a solid line represents an composition.
- An empty diamond (or white diamond) with a solid line represents a aggreation.
- A circle with a plus sign represents a containment.