Signal Start Event
A Signal Start Event launches a process instance when a broadcast signal is received. Unlike messages, signals are not targeted at a single recipient—they can trigger multiple processes simultaneously, enabling cross-process coordination.
What is a Signal Start Event?
A Signal Start Event starts a new process instance when a named signal is broadcast within the BPMN engine. Signals are a publish-subscribe mechanism: any number of processes or event handlers listening for the same signal name will be triggered simultaneously.
Visual Representation
The Signal Start Event is shown as a thin circle containing a triangle icon (pointing upward). The triangle distinguishes it from message (envelope) and timer (clock) start events, visually representing the broadcast nature of signals.
Key Characteristics
- Broadcast delivery: A single signal can start multiple process instances across different process definitions
- Loosely coupled: The signal sender does not need to know which processes are listening
- Named signals: Processes subscribe by signal name, enabling flexible event-driven architectures
- Cross-process coordination: Ideal for orchestrating reactions across independent business processes
Common Use Cases
Cross-Department Notifications
A regulatory change signal triggers compliance review processes in legal, finance, and operations departments simultaneously.
System-Wide Escalation
A critical system alert signal starts incident response, customer notification, and executive escalation processes in parallel.
Event-Driven Order Processing
A new-order signal starts fulfillment, billing, and customer communication processes independently without tight coupling.
Frequently Asked Questions
Related BPMN Elements
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