Classes' diagrams

Associations are relations (and also particular classes) between two classes.

Associations and aggregation

Associations have:

• A name (optional)
• Roles for each extremity (optional)
• Multiplicity/cardinality that restrict the number min..max of links (default is 1..1)

Associations can also:

• Have navigability to restrict the messages' flow (eg. only from Group to Element in the figure)
• Be a Composition (or aggregation) to stipulate, for instance, that the elements of a group must be destructed when this one is deleted.