Short Note on Activity and Swimlane Diagram

An Activity in the activity diagram is also known as Activity state. It is used to represent the invocation of operation, a step in an entire business process. Swimlane is a way in which the performed activities can be grouped by the same actor on an Activity diagram. To use swimlanes in an activity diagram, we need to arrange the activity diagram into vertical zones that are separated by the lines. This swimlane diagram places the steps of process within the horizontal or vertical swimlanes of workgroup or department using the metaphor of lanes in the pool. It provides clarity and accountability.

The activity diagram is a type of specific Unified Modeling Language (UML) Diagram that can optionally contain swimlane that means it’s not mandatory for the Activity diagram to contain Swimlane. So, we can say that an activity diagram can be a swimlane diagram. On the other hand, Swimlane is not a part of the term UML.

Let us understand the activity and swimlane diagram with an example.

  1. Activity Diagram –
    It is the essential diagram in Unified Modeling Language (UML) and is also known as object-oriented flowchart. It simply describes the positive and productive features or parts of a system. It is basically used for representing the flow of interaction from one activity to another in the form of graphical representation. It is described as an operation of the system and also used to capture the dynamic behavior of the system. Here, activity is referred to as the operation of the system.


    It allows us to create and make an event as an activity that usually contains numerous collections of nodes joint by edges. These diagrams are generally used to model Use cases, Classes, Interfaces, Components, Collaborations, etc. For understanding the diagram, we need to read it from top to bottom. Using an activity diagram, we can visually represent the workflows.

    Structure of the Activity Diagram :



    For example, below is an Activity Diagram for Reserving a Ticket.

  2. Swimlane Diagram :
    It is also a graphical representation of the System. Swimlane diagrams are also known as the Rummler-Brache diagram or a cross-functional diagram. Swimlanes are sometimes called functional bands. It simply describes who is responsible for the activities being performed in the activity diagram and how they are responsible. The activity diagram only represents the activities being performed, but Swimlane describes who does what in a process or activity performed.


    In the Swimlane diagram, the activity diagram is divided according to the class responsible for working or performing out these activities. It simply shows the connection and strong communication between these lanes and is used to highlight waste, redundancy, and inefficiency in a process of an activity or program.

    For example, below is a Swimlane diagram for reserving a ticket.

    Essential key-points of all the above diagrams :

    • Fork –
      It is used to represent the multiple parallel flows.
    • Branches –
      It allow the parallel flow within activities.
    • Merge –
      It brings together or combines together multiple branches.
    • Join –
      It is used to control and synchronize various parallel flows.

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