What is an activity diagram?

An activity diagram is an extension of the workflow diagram, visually depicting the flow of system operations as a sequence of actions.

For as long as people have been travelling from point A to point B, they've relied on maps to help them find their way. Workflow diagrams (also called flowcharts) fulfil a similar function, detailing every step that a process takes, including dependencies, responsibilities and tools. This allows users to logically plot out effective workflows, eliminate inefficient steps and blockers, collaborate among teams and see possible next steps at every stage of a project.

For an example of a workflow design tool that uses workflow diagrams, see ServiceNow Flow Designer. Flow Designer enables both professional developers and low-code business analysts to automate and integrate any business process as a digital workflow using natural language.

Activity diagrams take this concept further; an activity diagram is a Unified Modelling Language (UML) behaviour diagram that represents the workflow of activities within a system, using formally specified notation, symbols and rules. An Activity Diagram in UML is generally used in modelling software systems; they are considered behavioural diagrams, because they describe what must happen in the systems, they are modelling.

As with flowcharts and other diagrams, activity diagrams are a way to visually represent dynamic behaviour within a system. Activity diagrams depict the flow of programmes on a high level, allowing users to more clearly understand the conditions and constraints associated with specific operations, and to see message flow between activities.

Creating an activity diagram in UML makes it possible for users to model and diagram both conditional and parallel behaviour. The flow of an activity can be managed using various control elements in the UML flow diagram. In terms of usage, activity diagrams are uniquely suited for:

  • Modelling use cases and the steps they consist of.
  • Detailing software protocol as a permissible sequence of interactions between components.
  • Modelling software algorithms.
  • Charting business workflows among multiple users in a system.
  • Modelling the execution flow between system entities.
  • Present detailed information about functions or algorithms in the system.
  • Create a high-level understanding of system functionalities.

As with any kind of business-process diagram, the main benefit of using an activity diagram is improved process visibility and clarity. Users can take in and briefly understand the relationship between objects, including how they flow together. They can also see where different responsibilities and dependencies lie, and where important decisions lie must be made. Likewise, diagramming is beneficial to collaboration and documentation, communicating processes in a way that is easily shareable across teams and departments.

In addition to these benefits, activity diagrams can help businesses accomplish the following:

  • Demonstrating the logic of an algorithm.
  • Describing the steps performed in a UML use case.
  • Illustrating workflows between users and systems.
  • Simplifying and improving processes by clarifying potentially complex use cases.
  • Modelling software architecture elements, including function, method and operation.
Activity Diagram Benefits - ServiceNow

Although activity diagrams follow standardised rules in UML, there is still some freedom in creating these diagrams, particularly in terms of what elements to include. Most commonly, activity diagrams include the following components:


Activities describe business processes, and include activity nodes and activity edges, allowing tasks to flow along a sequence.


An action is a task performed either by the software of the user. Actions begin when all input conditions have been met and use incoming and outgoing activity edges to specify the flow of control and data between activity nodes.

Activity edges

An activity edge is a direct connection between activity nodes, representing the path that a token can take between two activity nodes. The activity edge is responsible for continuing the flow towards the next action once the previous action has been completed.

Control flows

Control flows are connectors that visualise the flow between steps in the diagram.

Start nodes

The initial node at the beginning of the diagram, the start node represents the starting point of the activity.


A decision is a point in the diagram where the user or the software has a choice to make. Each option leads to a new branch, so the decision is made up of one input, and at least two outputs.


Merges are the opposites of decisions, bringing together multiple branches or flows into a single point. A merge is made up of at least two inputs and only one output.

End nodes

The end node is the final step in the activity; completion of the end node denotes that the activity has likewise been completed.

ServiceNow, the industry leader in IT management, is bringing the benefits of advanced activity mapping to businesses across the globe. Built on the award-winning Now Platform, ServiceNow Process Automation allows organisations to create detailed process flows using data from audit trails, for easy, yet in-depth business process analysis. Eliminate process bottlenecks, uncover hidden inefficiencies, see detailed visual representations of your process and activity flow, and create a complete map of each connection, dependency and relationship. Process Automation makes it all possible.

With Process Automation, organisations have an easy-to-use solution for fast, accurate and cost-effective diagramming. More specifically, companies that use ServiceNow Process Automation tend to enjoy the following advantages:

Optimised processes

Place vital processes and all their corresponding tasks, activities, actions, responsibilities and dependencies under a microscope. Unmatched process visibility makes it possible to continually measure and improve service delivery to align with SLAs and customer expectations more closely. With ServiceNow, the act of optimising processes is ongoing and effective.

Better performance monitoring

Processes aren’t the only aspects that stand to improve from Process Optimization; employees, agents and others who are involved in relevant processes will have a more-detailed view of their own performance. Process Optimization makes it possible to see and compare effectiveness across an organisation, so that leaders and employees can take steps to improve results for workgroups and tasks.

Improved productivity

By streamlining business processes, ServiceNow Process Optimization allows organisations to cut away unnecessary elements and provide employees and machines with a straight-forward, easy-to-follow sequence of steps to reach activity completion. This frees up resources and gives businesses a chance to apply those resources to other projects and tasks, improving productivity across the board.

Increased efficiency

Along with increased productivity, the ability to eliminate unnecessary variants from core business processes also helps reduce investment costs. Organisations can do more with less, for increased business-process efficiency.

Faster results

Streamlined processes mean faster solutions. And, by integrating with ServiceNow Continual Improvement Management and other ServiceNow apps, organisations can improve their workflows faster than ever before.

Explore Process Optimization

Learn more about Process Optimization and put the world’s most advanced workflow and activity diagramming tools to work for you.

Loading spinner