Message Event

Introduction to BPMN Message Events

In the Business Process Model and Notation (BPMN) standard, a message represents a form of communication between two participants in a process. This communication is modeled as a message event within BPMN diagrams, which can either be a catching or throwing (sending) event. Messages are fundamental in depicting the flow of information across different parts of a process or between different processes.

Differences Between Catching and Sending Messages

  • Catching Message Event: Represents a point in the process where it waits to receive a message. Symbolized by a single thin outline.

  • Sending Message Event: Indicates where a message is sent from the process to an external participant. Depicted with a double outline.

Modeling Messages in BPMN

BPMN models messages with specific icons to differentiate between catching and sending events, ensuring clear communication and coordination between different parts of a process or across multiple processes.

Restrictions Provided by the BPMN Standard

  1. Correlation: Ensures messages are delivered to and received by the correct process instances.

  2. Instantiation: A start message event can initiate a new process instance with a defined message.

  3. Unidirectional: Messages are unidirectional, meaning they can only be sent from one process instance and received by another.

Configurations for Message Events

Symbolized by the following pictograms:

  • message icon

We can distinguish between the following message events:

  1. Catch Message Start Event: A start event can only receive a message

    • Catching start message event

  2. Intermediate Message Event: An intermediate event can send or receive a message

    • Intermediate throwing message event

    • Intermediate catching message event

  3. End Message Event: An end event can only send a message

    • End message throwing event

Creating a message

To create a message, you must first define the message in the general tab of the properties panel:

message creation

(1) - Automatically generate a message by clicking on the + icon.

(2) - Allow you to search model from other BPM models. Message from other models

(3) - Display the newly created message or search for existing messages in the BPM model.