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Message Throw Event

A Message Throw Event is a BPMN event that sends a message to another process, participant, or external system during the execution of a process. It represents an explicit point in the process where communication is initiated.

Message Throw Events are used to model process-to-process communication, system integration, and event-driven interactions where the current process actively sends information outward.

Key characteristics​

  • Actively sends a message:
    When the event is reached, a message is sent to a defined recipient. The process does not wait for a response unless explicitly modeled elsewhere.

  • Does not terminate the process (except End Event variant):
    In its Intermediate form, the process continues after the message is sent.
    In its End Event form, the message is sent and the process (or token) is terminated.

  • Requires a defined message: Must reference a BPMN Message (messageRef) that defines the payload and semantic meaning of the communication.

  • Asynchronous by nature: Sending a message does not imply synchronization or guaranteed immediate reception. Delivery semantics depend on the execution engine and integration setup.

  • A logical receiver expected: The message should be intended for a known receiver, such as another process, a participant in another pool, or an external system.

Variants of Message Throw Events​

  • Intermediate Message Throw Event:
    Sends a message during the process flow and then continues execution.

  • Message End Event:
    Sends a message and immediately ends the process or token.

Graphical notation​

  • Intermediate Message Throw Event:
    A double-line circle with a filled (black) envelope icon inside.

  • Message End Event:
    A bold single-line circle with a filled envelope icon inside.

Message throw event usage example

XML Definition​

Message definition​

<bpmn:message id="Message_OrderSent" name="Order Sent" />

<bpmn:intermediateThrowEvent id="ThrowMessage_1" name="Send Order">
  <bpmn:messageEventDefinition messageRef="Message_OrderSent" />
</bpmn:intermediateThrowEvent>

<bpmn:endEvent id="EndEvent_Message_1" name="Send Completion Message">
  <bpmn:messageEventDefinition messageRef="Message_OrderSent" />
</bpmn:endEvent>