The Sequence diagram is a type of Interaction diagram that focuses on the Message interchange between various Lifelines.
A Sequence diagram shows the interaction information with an emphasis on the time sequence. The diagram has two dimensions: the vertical axis representing time and the horizontal axis representing the participating objects. The time axis could be an actual reference point by placing the time labels as text boxes. The horizontal ordering of the objects is not significant to the operation, and you can rearrange them as necessary.
SequenceDiagram.org is an online tool / software for creating UML sequence diagrams. Founded in 2014 with the purpose to improve the efficiency when creating and working with sequence diagrams by combining text notation scripting and drawing by clicking and dragging in the same model.
- Sequence Diagrams Dan Fleck Interaction Diagrams UML Specifies a number of Interaction diagrams to model dynamic aspects of the system Model dynamic aspects of the system Messages moving among objects/classes Flow of control among objects Sequences of events Dynamic Diagram Types Interaction Diagrams Set of objects or roles and the messages that can be passed among them.
- Since the core components are the messages that are exchanged between objects, we can build communication diagrams the same way we would make a sequence diagram. The only difference between the two is that objects in communication diagrams are shown with association connections.
- Sequence diagram is an absolute must when designing a new feature you add to the system. It shows the affected parts of the system, points of integrations with external software and contracts which the team will have to create or update. Sequence diagram is valuable for QA engineers as well.
- When drawing a sequence diagram, remember that lifeline notation elements are placed across the top of the diagram. Lifelines are representative of roles or object instances that partake in the sequence being modeled. From a visual perspective, lifelines are shown as a box with a dashed line descending from the center of the bottom edge.
There are two Sequence Diagram modeling approaches:
- Activation bars as the lifelines.
- Activation bars as the Execution Specifications (new modeling approach).
Sequence Diagram Components List
The purpose of the Sequence diagram is to represent some aspect of the communication between objects to perform a task. The main benefit of the diagram is that it helps to identify the messages exchanged between objects.
A Sequence diagram can be used to:
- represent the details of a UML Use Case
- model the logic of a sophisticated procedure, function, or operation
- analyze the interaction of objects and components to complete a process
- plan and understand the detailed functionality of an existing or future scenario.
Sequence diagrams are valuable because they:
- allow seeing the specific questions, commands, and data being communicated during the execution of a specific task
- identify the communication required to fulfill an interaction
- identify the objects that participate in an interaction
- identify the data that is passed as part of the interactions.
Example of a Sequence diagram
- Working with Execution Specifications
Sequence Diagram Tool
|Notation Description||Visual Representation|
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