UML Diagram

Association symbols

• Extend: empty triangle head

• Implement: empty triangle head, dash line

• Abstract Name: italic font

• Association: simple arrow

• Depend: simple arrow, dash line

• Composition: simple arrow, diamond back

  • Implies ownership
  • Contained object cannot exist without the container. e.g., Transport cannot function without Engine

• Aggregation: simple arrow, empty diamond back

In UML, here are the three relationship types with their key differences:

Relationship	Question	Example	Notation
Association	”Does A use/know B?”	Customer → Order	Simple arrow
Aggregation	”Does A have B, but B can exist alone?”	Team → Player	Simple arrow Empty diamond back
Composition	”Does A own B, and B dies with A?”	Car → Engine	Simple arrow Filled diamond back
Extend			Empty triangle head
Implement			Empty triangle head Dashed line