Use Case Relationships

• Communicates - Participation of an actor in a use case;
• Generalisation - Inheriting parent behaviour, adding and overriding with the child's own behaviour;
• <<include>> Relationship - One Use Case including another use case to include the latter's behaviour
• <<extend>> Relationship - One Use case is extended to another use case so that the latter has the behaviour of the former in addition to its own; extension can only be done at extension points of the use case being extended.