Events in BPMN

Events represent something that happens during a process. Events can start, interrupt, delay, or end the process flow. In BPMN, each event is defined by its type (start, intermediate, end) and trigger (e.g., message, timer, error). This page describes how events should be modeled in Maestro diagrams, independent of execution support.

Modeling recommendations

• Prefer descriptive labeling on all events to indicate business meaning (e.g., Timeout after 2 days instead of Timer).
• Use signal events only for loose coordination; avoid using them to enforce logic.
• For large diagrams, use link events to avoid clutter caused by long flows.
• Do not overuse intermediate events. Focus on clarity over completeness.

Start events

A start event defines how a process begins. A diagram must include at least one start event.

Event type	Icon	Meaning
None		Used for manual starts or when the trigger is defined outside the BPMN model.
Message		Indicates the process is triggered by an incoming message. Often used in called processes.
Timer		Indicates the process starts at a specific time or after a delay. Useful for scheduled operations.

You can model multiple start events in the same process to support different entry points.

When you have multiple start events and you want to do a Debug, right-click the start event you want to test and select Test.

When you deploy a process, you can set a default entry point (a start event). Orchestrator uses this start event when you start the process without explicitly specifying one. You can still run or debug from any other start event by selecting it at run time.

Note: A process in Maestro must include at least one start event. You can model multiple start events within the same process to support different entry points (for example FHTTP/API), scheduled, or manual triggers. Use sub-processes to model additional entry points.

For more details about the BPMN elements supported in Maestro, see BPMN support.

Intermediate events

Intermediate events model things that happen between the start and end of a process. They can delay the flow, wait for an input, or signal something to other elements.

Event type	Icon	Usage
Message (Catching)		Waits for a message to continue. Placed inline or on a boundary.
Timer		Delays flow until a timestamp or duration. Commonly used for timeouts.
Signal (Throw/Catch)		Broadcasts or waits for a signal. Use to loosely couple process fragments.
Link (Throw/Catch)		Used as off-page connectors. Improves readability in large diagrams.
Escalation (Throw/Catch)		Indicates a business-level escalation. Typically attached to boundary events.
Error		Represents an exception. Must be caught by an error boundary event on a task or sub-process.

Important: In modeling, intermediate events should be used to clarify dependencies or timing logic. The actual behavior may depend on runtime support.

For more details about the BPMN elements supported in Maestro, see BPMN support.

Boundary events

Boundary events are attached to tasks or sub-processes to model interruptions or timeouts.

Event type	Icon	Behavior
Interrupting timer		When the timer fires, cancel the attached task/sub-process and follow the boundary flow. Use for timeouts, SLAs, or deadlines. If you need the activity to continue, use a non-interrupting timer boundary event.
Interrupting error		Catches an Error thrown by the attached activity or its inner work, cancels that activity, and routes to the boundary flow. In BPMN, error boundary events are always interrupting. Common with Call Activities to handle errors from a called process.
Escalation		Catches an Escalation from within the attached activity. If marked interrupting, it cancels the activity; if non-interrupting, it starts the boundary flow in parallel while the activity continues. Use to notify or raise attention without treating it as a failure.

Important: Use boundary events to represent expected exceptions or alternate flows. Place them visually on the edge of the task they monitor.

For more details about the BPMN elements supported in Maestro, see BPMN support.

End events

End events indicate how a path terminates. Each path in a diagram should end with one

Event type	Icon	Meaning
None		Used for manual starts or when the trigger is defined outside the BPMN model.
Message		Indicates the process is triggered by an incoming message. Often used in called processes.
Error		Indicates the process starts at a specific time or after a delay. Useful for scheduled operations.
Terminate		Immediately ends the entire process instance, canceling all active paths,

Important: Use end events consistently to signal completion or failure. Avoid leaving paths open.

For more details about the BPMN elements supported in Maestro, see BPMN support.

Special event types

The following event types can appear as intermediate, boundary, or end events, depending on usage. These events typically model waiting, signaling, exceptions, or off-page navigation. They are supported for modeling clarity in Maestro.

Event types	Description	Typical use	Execution in Maestro
Timer	Waits for a specific time, duration, or cycle	Deadlines, delays, timeouts
Signal	Broadcasts or receives a named signal across process boundaries	Loose-coupled notification
Error	Interrupts the current activity or path due to an exception	Business errors, validation failures
Link	Connects different parts of a process, often across pages	Improves readability, avoids long arrows

Modeling guidelines

• Timer Events: Use as intermediate or boundary events to represent time-based control (e.g., Wait 2 days, Escalate after timeout).
• Signal Events: Use to coordinate across disconnected paths or sub-processes. Avoid relying on signal order or delivery timing.
• Error Events: Use on boundary events to redirect the flow on failure. Also valid as end events when explicitly terminating with an error.
• Link Events: Always pair a throw and a catch. Useful for breaking up complex diagrams into readable sections.

Important: All of these events are supported in Maestro for both modeling and execution, except where noted. Label each clearly to reflect its business intent.

For more details about the BPMN elements supported in Maestro, see BPMN support.