Message Start Event
A Message Start Event initiates a process when a specific message is received from an external participant. The process instance is created only when the expected message arrives, enabling event-driven process automation. For example, a claims handling process starts automatically when an insurance claim email arrives from a customer. For example, when a customer submits an online order, the order message triggers a new fulfillment process instance that handles picking, packing, and shipping.
What is a Message Start Event?
A Message Start Event triggers a new process instance when a message is received from outside the process boundary. This enables processes to start automatically in response to external communications-emails, API calls, system notifications, or inter-process messages.
Visual Representation
The Message Start Event is depicted as a thin circle (like all start events) containing an envelope icon. The envelope is unfilled/outlined, distinguishing it from the filled envelope in Message Throw Events.
Key Characteristics
- External trigger: The process waits for and starts upon receiving a specific message type
- Message correlation: Messages are matched to processes using correlation keys (order ID, customer ID, etc.)
- Single instance per message: Each received message creates exactly one process instance
- Multiple message starts: A process can have several Message Start Events, each listening for different message types
See it in action
A supplier process starts when a message arrives from the cosmetics company
Read: Beauty Paradise →Common mistake
Not defining a clear message name/type. If multiple Message Start Events exist in a process, each must listen for a different named message or the engine cannot determine which one to trigger.
How it connects
Common Use Cases
Order Processing
A fulfillment process starts when an order confirmation message is received from the e-commerce platform.
Customer Support Ticket
A support workflow initiates when a new ticket message arrives from the helpdesk system or email gateway.
Integration Webhook
A data synchronization process begins when a webhook notification is received from a third-party service.
Frequently Asked Questions
Related BPMN Elements
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