A Sequence diagram is a structured representation of behavior as a series of sequential steps over time.
- Depict work flow, 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
- Each sequence element is 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 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
To toggle the numbering of messages on a Sequence diagram, select or deselect the Show Sequence Numbering checkbox on the Options dialog.
Example Diagram: Example Sequence Diagram
Select Sequence diagram elements and connectors from the Interaction pages of the Toolbox. Click on the following elements and connectors for more information.
- Denote the Lifecycle of an Element
- Layout of Sequence Diagrams
- Sequence Element Activation
- Lifeline Activation Levels
- Message Label Visibility
- Change the Top Margin
- Change the Timing Details
- Business Modeling/Interaction
- Sequence Diagrams and Version Control
- Show Sequence Numbering