Sequence diagrams A sequence diagram shows the sequence of messages exchanged by the set of objects performing a certain task The objects are arranged horizontally across the diagram An actor that initiates the interaction is often shown on the left The vertical dimension represents time A vertical line, called a lifeline, is attached to each object or actor The lifeline becomes a broad box, called an activation box during the live activation period A message is represented as an arrow between activation boxes of the sender and receiver - a message is labelled and can have an argument list and a return value www.oseng.com O Lethbridge/Laganiere 2001 Chapter 8: Modelling Interactions and behaviour© Lethbridge/Laganière 2001 Chapter 8: Modelling Interactions and Behaviour 7 Sequence diagrams A sequence diagram shows the sequence of messages exchanged by the set of objects performing a certain task • The objects are arranged horizontally across the diagram. • An actor that initiatesthe interaction is often shown on the left. • The vertical dimension representstime. • A vertical line, called a lifeline, is attached to each object or actor. • The lifeline becomes a broad box, called an activation box during the live activation period. • A message is represented as an arrow between activation boxes of the sender and receiver. —A message is labelled and can have an argument list and a return value