UML sequence diagram

Date: February 1st 2016
Last updated: February 1st 2016

A UML sequence diagram illustrates interactions and processes between objects and events. Importantly, a sequence diagram maps out messages (communication) that are sent between objects over a time sequence.

Sequence diagrams:

• Include two elements: messages and lifelines.
• Messages annotate communication
• Lifelines (annotated box with a hanging dashed line)
• Lifelines point to boxes representing length of time
• If theres no box, communication is idle
• Solid arrows refer to method call
• Dashed arrows refer to method return values