Sequence Diagram¶

A Sequence diagram is a structured representation of behavior as a series of sequential steps over time. You can use it to:

Depict workflow, Message passing and how elements in general cooperate over time to achieve a result
Capture the flow of information and responsibility throughout the system, early in analysis; Messages between elements eventually become method calls in the Class model
Make explanatory models for Use Case scenarios; by creating a Sequence diagram with an Actor and elements involved in the Use Case, you can model the sequence of steps the user and the system undertake to complete the required tasks

Construction¶

Sequence elements are arranged in a horizontal sequence, with Messages passing back and forward between elements
Messages on a Sequence diagram can be of several types; the Messages can also be configured to reflect the operations and properties of the source and target elements (see the Notes in the Message Help topic)
An Actor element can be used to represent the user initiating the flow of events
Stereotyped elements, such as Boundary, Control and Entity, can be used to illustrate screens, controllers and database items, respectively
Each element has a dashed stem called a Lifeline, where that element exists and potentially takes part in the interactions