Sequence Diagrams

Sequence diagrams are used to create one scenario of events through a use case. The objects associated with this series of events and the interactions between the objects are identified. These interactions are characterized by messages sent between the objects, but sequence diagrams do describe how the objects are linked.

Objects in a sequence diagram are arranged in columns on the horizontal axis of the diagram. Each object is represented with the object name inside of a rectangle. The object's label takes the form of ClassName:objectName. An external object that interacts with the system is represented by a stick figure. A vertical line is dropped down from each object. This vertical line represents the lifeline of the object in the system.

Time is represented by the vertical axis of the diagram. A message is represented by an arrow that points to the receiver. An object may send a message to itself. The message is labeled with the name of the message that is being passed, and any other arguments associated with the message.

Author: Laurie Williams and Sarah Heckman
Maintained By: Sarah Heckman
Last Updated: 2008-08-14