Actors
An actor in a UML diagram represents a type of role where it interacts with the system and its objects. It is important to note here that an actor is always outside the scope of the system we aim to model using the UML diagram.
We use actors to depict various roles including human users and other external subjects. We represent an actor in a UML diagram using a stick person notation. We can have multiple actors in a sequence diagram.
For example:
Here the user in seat reservation system is shown as an actor where it exists outside the system and is not a part of the system.
Sequence Diagrams | Unified Modeling Language (UML)
Unified Modelling Language (UML) is a modeling language in the field of software engineering that aims to set standard ways to visualize the design of a system. UML guides the creation of multiple types of diagrams such as interaction, structure, and behavior diagrams. A sequence diagram is the most commonly used interaction diagram.
Interaction diagram
An interaction diagram is used to show the interactive behavior of a system. Since visualizing the interactions in a system can be difficult, we use different types of interaction diagrams to capture various features and aspects of interaction in a system.
- A sequence diagram simply depicts the interaction between the objects in a sequential order i.e. the order in which these interactions occur.
- We can also use the terms event diagrams or event scenarios to refer to a sequence diagram.
- Sequence diagrams describe how and in what order the objects in a system function.
- These diagrams are widely used by businessmen and software developers to document and understand requirements for new and existing systems.
Important Topics for the Sequence Diagrams
- Sequence Diagram Notation
- Actors
- Lifelines
- Messages
- Create message
- Delete Message
- Self Message
- Reply Message
- Found Message
- Lost Message
- Guards
- How to create Sequence Diagrams?
- Use cases of Sequence Diagrams
- Challenges of using Sequence Diagrams
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